How to galvanize metal

Metal galvanizing

Galvanizing of metal is a modern, effective way to protect almost any metal product from the destructive effects of corrosion, increase service life with a guarantee of reliable operation. The method is applicable mainly to flat or slightly curved surfaces that are not subject to mechanical stress. Applying zinc to metal involves covering its surface with a special solution with a high zinc content (from 80 to 95%).

This was the case until Russian scientists discovered a gas-dynamic method of applying zinc to metal and developed the unique Dimet equipment, with the help of which the process of galvanizing metal became more accessible and perfect, and also overcame numerous limitations in application.

Why zinc?

The protective qualities of zinc are due to its chemical properties. Like aluminum or tin, zinc oxidizes upon contact with air, creating a dense film of oxidized molecules on its surface, which does not allow air to penetrate into the deeper layers of the metal, thereby protecting it from corrosion.

Standard methods of galvanizing metal

Zinc can be applied in several ways, each of which has its pros and cons. Currently, the following technologies are most widely used:

• Cold method;
• Hot;
• Electroplating;
• Thermal diffuse;
• Gas thermal.

The choice of method for spraying zinc onto metal depends on:

• Conditions for further operation of the coated metal parts;
• Parameters of the protective layer that is planned to be obtained;
• Conditions for applying zinc to steel (at home, in a workshop, in a production workshop, etc.);
• Features of the products to be coated: oversized, complex shape, assembled (non-disassembled), etc.

But no matter which method of coating the metal with a layer of zinc you choose, in any case, further mechanical impact on the treated surface is not implied.

Features of metal coating with a layer of zinc

1. Cold galvanizing:

«+» Allows you to obtain a fairly durable protective layer on the metal surface relatively simply.

«+» No special equipment is required, so the method is quite applicable at home.

«+» The zinc solution is applied using a spray gun or a regular brush.

«+» The solution used is zinconol and similar compounds that are commercially available.

«-» The zinc coating obtained in this way cannot be called particularly durable.

«-» It is unstable to mechanical stress, as well as metal expansion as a result of temperature changes.

«-» Organic solvents are used, which requires strict adherence to safety rules during the procedure.

This method is most often used for galvanizing products that cannot be coated with zinc in any other way. For example, for objects that are in an assembled state: pipelines, power lines, car bodies, etc.

2. Hot-dip galvanizing is quite popular in industrial production, but has many disadvantages, including:

«-» High risks of harm to personnel health and the environment due to the use of toxic chemicals at the metal preparation stage, as well as due to high temperatures when immersing the metal in a bath of molten zinc.

«-» The method is quite expensive.

«-» Requires the use of special technological equipment, and therefore cannot be reproduced either at home or in small services such as service stations.

«-» The main disadvantage of this method, which limits its use even in industrial conditions, is the size of the bath of molten zinc. If the product that needs to be galvanized is larger than the bath, then this method will not work.

3. The galvanic method consists of electrochemical action on the surface of the metal, resulting in the formation of a very smooth film of the required thickness. On average, its thickness reaches 20-30 microns maximum.

«+» The resulting coating is characterized by exceptional decorative properties and uniformity, as well as high adhesion (bond) to the metal.

«+» It is quite applicable at home or at small service stations.

«-» But achieving perfect adhesion is almost impossible due to the presence of all kinds of oxide and grease stains on the metal surface.

«-» The method requires the use of special equipment (a bath of electrolyte solution connected to the anode and cathode).

«-» The main disadvantage - the high cost - makes most people refuse to use it.

4. The gas-thermal method of galvanizing a metal creates a protective film on its surface by spraying heated zinc molecules from powder or wire in a gaseous environment.

«+» The finished protective layer created in this way reliably protects the metal from corrosion even when used under rather aggressive environmental conditions: excessive humidity, sea or fresh water.

«-» Hitting the metal surface, zinc molecules form a protective film with numerous pores, which are subsequently covered with a paint layer.

5. Thermal-diffusion galvanizing, or sherardization, is quite popular today, but due to its characteristics it is not applicable at home.

«+» The method is quite environmentally friendly, as it does not require waste disposal and is performed inside a sealed container.

«+» Allows you to maintain the exact parameters of a complex-shaped product coated with zinc.

«+» The resulting coating has high adhesion, practically no pores, and is several times more durable and reliable than galvanic galvanization.

«-» Purchasing a special box capable of heating the air inside to 2600° and maintaining this temperature to treat the metal surface with gaseous zinc atoms is an idea that most small and medium-sized services refuse.

«-» The method has limitations, allowing the formation of a zinc coating of at least 15 microns in thickness.

«-» It does not have high productivity, which makes it uninteresting for mass production.

«-» It is dangerous because it requires treating the metal surface with acid as preparation and leaves zinc particles in the air.

«-» Does not guarantee uniform thickness of the protective zinc film.

Processing metal with zinc at home

The easiest way to galvanize metal at home is cold. Another, available at home, but requiring technical preparation, is electrochemical. Both the first and second have a lot of disadvantages:

• Does not provide maximum strength of zinc coating;
• Does not guarantee high protective film adhesion to metal;
• Does not allow achieving a protective coating thickness of more than 20-30 microns;
• High cost of galvanization;
• The need to work with toxic chemical solutions.

In other words, cold and galvanic methods do not produce coatings similar to those obtained using industrial galvanizing methods. These are the main reasons why they were abandoned in car services, home workshops, as well as in industrial production and when performing repair, construction or installation work.

However, the creation of technical conditions for performing thermal diffusion, gas-thermal and hot galvanizing methods of metal is often impractical neither for financial reasons nor for considerations of labor costs, time costs and labor productivity.

As a result of the demand for high-quality, durable and reliable zinc coating of metal using a more economical, environmentally friendly, safe, practical and convenient method and the lack of supply, a unique development of Russian scientists was born - a gas-dynamic method of applying zinc to metal using Dimet equipment.

Its use provides high-quality and durable zinc coating without requiring significant financial, time and personnel costs, the creation of special conditions, the involvement of special personnel or additional equipment.

What is Dimet?

This is innovative equipment that sprays zinc molecules using a gas-dynamic method. It is actively used in domestic and foreign industry, auto repair shops, and home use.

Spraying of zinc onto metal using the gas-dynamic method using the Dimet installation is carried out using zinc molecules (from powder) with a narrowly directed jet of heated compressed air at supersonic speed. Zinc molecules supplied in this way reliably adhere to the surface of almost any metals and alloys.

Advantages of use:

• Increased efficiency due to low consumption of sprayed material.
• Environmental friendliness: when used, it does not form compounds harmful to health.
• Manufacturability: does not require the creation of special conditions of use or the use of additional equipment.
• Convenience and practicality of using the equipment when working with any metal surfaces, several operating modes, the ability to use both indoors and outdoors, compact dimensions, mobility and light weight.
• Efficiency due to the unique technology of metal spraying, capable of restoring almost any metal surface accurately, without subjecting it to excessive heat, over a wide temperature range.
• Safety of use, since during use the flow of zinc molecules is narrowly directed and affects only a certain area of ​​the surface. The adjacent areas completely retain their original appearance, as they are not affected or deformed.
• Versatility of use due to the deposition of not only zinc, but also other metals. And also effective when processing almost any alloys and metals, including cast iron.

Where is it used?

The scope of application of Dimet equipment is practically unlimited: both in industry and in services of any format, including home workshops. Using the gas-dynamic method of zinc spraying using the Dimet installation, the following is performed:

• Restoration of parts that have failed due to deformation or wear;
• Application of electrically conductive coating to metal parts and elements;
• Spraying a thin layer of material for subsequent soldering of parts;
• Applying a protective coating to internal and external elements of engines;
• Corrosion protection of stationary objects and structures.

This is not a complete list of areas of application for Dimet installations, but it is quite sufficient to understand how irreplaceable and in demand they are in both industrial, commercial and home use.

Source: https://dymet.org/tehnologiya/tsinkovanie-metalla

Zinc spray metallization | Zinc portal

Zinc spray metallization is carried out by applying molten material to the surface to be treated using special equipment. The zinc spray metallization process is based on thermal atomization technology. The protective surface layer is formed from discrete particles (scales) that are in a molten or plastic state.

Zinc metallization by sputtering. Coating technology

Gas thermal spraying includes several sequential technological operations:

1) heating or melting by some heat source (depending on the equipment used) of the sprayed material,
2) transfer of dispersed (condensed) particles by a gas flow,
3) formation of a protective layer on the treated surface.

the surface to be treated in the form of molten or plasticized parts. The gas flow accelerates the movement of the sprayed material. When particles collide with the processed (metal) surface, they deform, cool, and form a protective layer. The structure of the surface coating has a scaly, layered structure.

The formed zinc layer is characterized by high porosity (0.5 - 30%) and adhesion strength of the sprayed material to the substrate (up to 280 MPa). Therefore, this technology is most often used to restore and strengthen critical parts and structures.

Classification of zinc metallization methods by sputtering

1. In the process of gas thermal spraying, a certain amount of energy is expended, which is necessary to melt the sprayed material and accelerate the formed particles. The following can be used as a source of thermal energy:

• the energy of chemical processes that is obtained

1) as a result of the process of oxidation (combustion) of fuel gases in the atmosphere, 2) during detonation of an explosive mixture,

3) as a result of combustion of the fuel mixture in the chamber (at increased pressure),

• Electric Energy:

1) electric arc, 2) plasma, gas flow,

3) ohmic heater,

• vibration energy (electromagnetic):

1) electromagnetic high-frequency field,
2) generator, quantum, optical.

2. The sprayed material can be used in different states of aggregation and have different appearances:

• powder mixture,
• wire,
• cord,
• rod.

3. The speed characteristics of sprayed particles have different effects on the formation of the surface layer (porosity, roughness, adhesion strength).

4. Thermal spraying can be carried out in various environments:

• in air,
• in vacuum,
• in a controlled atmosphere.

The listed criteria determine a wide variety of methods for applying a protective coating by spraying and create opportunities for the formation of a surface layer with different technological characteristics.

Advantages of zinc sputtering method

1. Spraying can be done on parts and structures of various dimensions and configurations.
Coverage area may vary. 2. During the coating process, the thickness of the zinc layer can be varied (0.01 - 10 mm).
3. The technological process can set various porosity parameters of the formed coating (up to 30% and above).
4.

Various materials can be used as a substrate for spraying: metal, glass, ceramics, plastic.
5. Coating can be applied in various climatic, temperature and aggregate (water, air, vacuum) conditions.
6.

The zinc gas turbine method is practically environmentally friendly and harmless (in the process of work, special filters are used that are capable of adsorbing harmful products of the technological process).
7. During the work process, simple, portable equipment is used.
8. Spraying can be done in several layers, which allows you to obtain a coating with special technological characteristics.

9. In the process of thermal spraying, the base of the part or structure to be coated is slightly deformed.
10. The technological process of zinc gas turbocharger is characterized by low labor intensity and high productivity.

Areas of application of products after galvanization

The method of gas thermal spraying with zinc is actively used in industrial production to restore worn parts of machines and equipment. The technology allows saving production resources. Refurbished parts have all original technological parameters and characteristics.

Thermal spraying also allows for the restoration of parts with visible cracks and chips. During the technological operation, surface damage is completely eliminated. High adhesion parameters between the base and the sprayed layer make it possible to restore the strength characteristics of a damaged product.

The main task of thermal zinc spraying (GTS) is to protect metal structures from corrosion damage. The technology of zinc metallization by spraying makes it possible to galvanize parts, structures and structures of various overall dimensions and shapes.

The unlimited possibility of coating treated surfaces using the zinc spraying method allows you to protect bridges, cranes, high-voltage electric masts, advertising boards and structures, road structures and much more from corrosion and extend their full service life.

Source: http://www.zinkportal.ru/cinkovaja-metallizacija-napyleniem/

Do-it-yourself metal galvanizing, galvanizing at home

Galvanizing metal in a modern car is an opportunity to protect the body surface from corrosion. Galvanizing metal with your own hands at home is a completely feasible task.

There are certain types of metal that, when in contact with air, form a protective film on the surface. It protects the material from environmental influences and prevents corrosion. On metal, which is used to produce cars, the film is weak, so it is not able to protect the product from destruction.

Industrial processing methods

You can create additional protection against corrosion in several ways, for example, by coating products with tin or zinc. Galvanizing a material is a fairly simple task and can be easily done with your own hands. Treatment of parts, for example for a car, will protect the surface of the products from direct contact with air, which prevents oxidation of the surface. Metal processing with zinc is possible in several ways:

• Hot and cold galvanizing.
• Galvanic.
• Gas-thermal.
• Thermal diffusion.

When processing a material using one of these methods, the duration and temperature of the process affect the thickness of the protective surface layer formed.

Hot-dip galvanizing technology

This method of metal processing is one of the most effective. Zinc remains on the surface for a long time and reliably protects against corrosion. The disadvantage of this treatment is that this technology is harmful to the environment since the material is processed chemically. Hot galvanizing of metal consists of several subsequent processes:

• Preparation. The surface of the parts must be degreased, and then the metal must be etched.
• Treatment. After preparation, the machine part must be washed and dried.
• Galvanizing. The product is lowered into a tank containing molten zinc.

This processing method, despite its effectiveness, has significant disadvantages:

• Galvanizing metal requires special equipment and containers.
• Impossibility of processing large-sized products, for example, car bodies.

Cold galvanizing technology

Galvanizing car parts using this method is quite simple. Surface treatment is carried out using a special paint containing zinc. The metal surface is painted with zinc paint using the usual painting method: with a brush, roller or spray gun.

Using zinc-containing powder paint and a spray gun makes galvanizing a vehicle easier. The spray gun allows you to completely treat the entire surface of the body, including hard-to-reach places. This method is most often used to apply a protective coating to products that are difficult to hot process. The car body is just such a case. This method is also used for processing previously galvanized metal.

Galvanizing technology

Galvanic deposition of zinc involves processing the metal using electrochemical action. Processing with this method allows you to achieve a smooth and thin protective layer on the surface of the product.

In order for the zinc to adhere to the surface, for example, of a car body, the products are placed in a special container in which a zinc plate is located.

After this, electricity is supplied to the container, as a result of which the zinc from the surface of the plate is transferred to the machine body, forming a protective layer.

The disadvantages of this method include its high cost compared to other methods of applying a protective layer. In addition, such treatment is dirty and wastewater treatment also requires high costs.

Gas-thermal galvanizing method

This method of applying protective coating is excellent for the body of large vehicles that cannot be treated using conventional methods.

Zinc is applied to the surface of the car body using a strong gas stream. The use of this method requires subsequent application of paint, since the zinc does not spread evenly on the surface and does not fill the entire surface of the car. But despite this, this method of creating protection provides reliable coverage. It protects the car both from air exposure and provides reliable protection against corrosion in wet conditions.

Thermal diffusion galvanizing method

Galvanizing a car body using this method involves the use of high temperatures. At a temperature of approximately 2.6 thousand degrees, zinc breaks down into atoms, which are deposited on machine parts. The advantage of this method is that it can be used to achieve a thick protective layer.

The process of applying protective material to the car body is carried out in a special closed chamber. Powdered zinc is applied to the product, after which the entire chamber is heated. This can only be done in an industrial environment, so you won’t be able to apply zinc yourself at home.

The use of this method is safe for the environment and allows for galvanizing of excellent quality. Zinc is applied to the surface of the machine in a thick layer, which will reliably protect metal products from corrosion. The method has only one drawback - its high price.

Galvanic method

Electroplating of a protective layer, for example, on car parts, can be done at home. To do this, you will need a car battery or power supply with characteristics of 2–6A and a voltage of 6 to 12 volts. To perform galvanic formation of a protective layer, you need to have an electrolyte. To make an electrolyte with your own hands, you need to make a solution using the following ingredients:

• 400 grams of zinc sulfate.
• 100 grams of ammonium or magnesium sulphate.
• 30 grams of sodium acetate.
• 2 liters of plain water.

Having prepared such a solution at home, you can galvanize the metal parts of the machine. Instead of the described solution, liquid from your car battery will also work. An ordinary glass jar is suitable as a container for the composition. The galvanizing process at home using the galvanic method looks like this:

• Cleaning and degreasing car parts.
• Immerse the workpiece in sulfuric acid for a few seconds.
• After repeated washing, the material is placed in a container for subsequent galvanizing.
• Secure the positive contact from the battery or power supply to a zinc plate.
• The negative contact should be attached to the workpiece.
• After this, place the zinc plate and the car part in a container with the solution and leave for 30 - 40 minutes.

When carrying out this operation at home, you should keep the windows open in the room, and also use special clothing and gloves. Using this set of devices, you can galvanize small products or car parts with your own hands. The method does not require much expenditure from you and is carried out quickly.

Cold galvanizing method

Galvanizing of machine parts can also be done using the cold galvanizing method. For this method, you need to purchase special paint containing zinc.

It is two-component, so before the galvanizing process, the paint components must be mixed together. A set of zinc powder and a binder must be mixed in a ratio of 3 to 1 or 1 to 1.

After mixing the paint, at positive air temperatures, apply the composition to the machine part. The cold method is very simple and easiest to do at home.

Despite the fact that galvanizing metal in an industrial environment is a complex process, you can galvanize products at home using simple methods.

Source: https://autolirika.ru/soveti/cinkovanie-metalla-svoimi-rukami.html

Galvanizing as a way to protect metal

Products made of metal may be subject to corrosion during use. In order to prevent the development of corrosion processes, and, accordingly, increase the service life of metal parts, manufacturers try to provide them with a special layer of protection.

World practice has shown that the most effective way to protect metal from the harmful effects of corrosion is galvanizing it. This process involves applying a special layer to the surface of the product, which consists of 95% zinc. Despite the fact that such a process is considered not too expensive, its efficiency is at a high level.

The operating principle of the process of processing metal products with zinc is based on the interaction of zinc with oxygen, after which a very thin oxide layer is formed on the metal. The main purpose of the film is to protect the metal surface from external factors.

Types of metal galvanizing

Galvanizing of metal products is designed to provide an electrochemical protective reaction and can be done in a variety of ways. Depending on a particular method of applying a layer of zinc to a product, various complex devices will be used, which, in turn, will affect the protective ability of the layer itself.

Before you begin the actual layering process, you need to choose a method. The choice is influenced by:

• Operating conditions for metal products.
• Properties that a layer containing zinc should have.
• Thickness of the formed surface.

When choosing a method for applying a galvanizing layer, do not forget that the protective layer of zinc is quite fragile and is easily subject to destructive processes. Therefore, parts or structures should be protected from significant mechanical influence.

The main types of galvanizing are:

1. Hot-dip galvanizing and its technology

This type is considered the most effective and durable option for providing protective properties to metal products from corrosion. Among the disadvantages of this method is only increased danger, because complex compositions with chemical reagents are used in the metal processing process.

Hot galvanizing of metal involves several stages:

• Preparatory. At this stage, the surface layer of the metal product is cleaned and degreased. This is followed by etching using acid-based solutions, the products are washed and fluxed.
• Basic. Having carried out all the preliminary procedures and thoroughly dried the metal, it is immersed in a bath where molten Zn is stored. As a result of the action of high temperatures, the element, together with iron, envelops the upper area of ​​the metal with a thin layer, leaving behind a layer of resistance to corrosion processes. When removing the part from the container, it is blown with compressed air using special equipment. Due to the blowing, the film dries completely and the excess is removed

Even if the dimensions of the parts are limited by the size of the bath used, the hot galvanizing process is widely used in enterprises producing metal structures and other large metal products. It will not be possible to use this method on your own, since it is not possible to use special equipment.

2. Gas-thermal galvanizing

This is how metal sheets or volumetric products are processed. The method is carried out by spraying dry Zn as part of a gas shell on the surface of the part, while molten metal particles hit the area, leaving a thin layer there.

The structure of the resulting layer should resemble porous scales, which creates a level of protection that allows the product to normally withstand aggressive influences for a long time.

3. Cold galvanizing of metal

This method is becoming widespread due to its sufficient manufacturability and ease of use.

The method is based on the moment of painting the treated surface with paint with a high percentage of the Zn-based powder mixture (89-93%).

Spraying occurs using a roller or brush, but the use of special sprayers is allowed, which reduces the time spent on applying the mixture. The surface is elastic, capable of withstanding complex deformation processes.

Among the disadvantages of this method are instability to the influence of mechanical processes and the need for special precautions, since an organic solvent is used.

4. Thermal diffusion galvanizing

The invention of this method occurred at the beginning of the last century. Its essence is to coat the top layer of a metal product with Zn by converting the atoms of the element into a vapor composition at temperatures above 26,000. This method allows Zn particles to penetrate into the iron, leaving behind a complex structure.

The galvanizing process in this case is similar to the hot-type process, but differs in that at the final stage the part is placed in a drum-type furnace, where, in fact, galvanization occurs.

Among the advantages of the thermal diffusion galvanizing method:

• Environmental Safety.
• High adhesive properties of the coating due to the complete absence of pores.
• High protective properties.
• Possibility to change the thickness of the coating during the application process.
• Possibility of application to parts with complex shapes.
• Waste does not require special disposal.

The disadvantages are:

• The coating lacks a decorative characteristic reflection.
• Relatively low productivity.
• Presence of harmful aerosols of dust particles Zn.
• The occurrence of defects in the form of uneven thickness.

5. Galvanizing

Galvanic galvanizing of a metal allows you to create the highest level of smoothness on its surface by influencing it with an electrochemical nature. Regardless of the current conductivity properties, this method can be applied to all materials, creating a layer with a thickness of 20 to 30 microns.

Electroplating-based galvanizing is carried out by immersing a metal product along with a Zn plate into a tank containing an electrolyte. This is followed by connection to the voltage, the Zn anode dissolves and it settles on the metal surface.

Among the advantages of this method:

• The presence of a beautiful decorative shine.

Among the disadvantages of the method:

• Quite a high production price.
• Generation of hazardous waste.

Galvanized steel also rusts

Galvanized steel today finds its wide application in roofing work. This material is a sheet coated with a thin layer of zinc, which should protect the metal from the occurrence of corrosive processes under the influence of an aggressive external environment. By increasing the metal's resistance to corrosion, Zn also increases the service life of the steel sheet.

But, despite the many advantages of using galvanized material, it also has some disadvantages, the main of which is considered to be corrosion of the Zn element.

And, answering the question of whether galvanized steel rusts, it is worth noting that a white powdery substance can appear on the surface of the zinc, which is called “white rust.”

In order to avoid the risk of such corrosion, it is recommended to coat galvanized steel with a special paint that can not only create external beauty, but also increase the service life of galvanized steel.

Galvanizing at home

Despite the fact that all methods of galvanizing metal products are quite complex, some of them can be carried out independently. For example, the most common method is cold galvanizing or, as it is often called, electrochemical.

Before you begin the galvanizing process itself, you should carefully prepare the surface, that is, clean it of foreign particles and degrease it well. Next, you should begin the process of etching with an acid composition and rinse thoroughly with water.

In order to galvanize metal on your own, you can make a special device with your own hands from a direct current source. In this case, the output voltage should be in the range of 6-12 V, and the current should be 2-6 A. Such a device should consist of:

• A container made of dielectric.
• Electrode fixing device

In this case, a solution of a salt of any origin containing zinc can act as an electrolyte. Some people prefer to prepare a solution from battery electrolyte by placing zinc in it and waiting for complete dissolution.

The thickness of the resulting layer is influenced by:

• Current density per unit area of ​​the processed product.
• The temperature of the solution that is used as the electrolyte.
• Density of the solution used.
• Shape, parameters and complexity of the geometry of the metal product being processed.

The zinc electrode in this case can be made from a piece of zinc with a hole drilled in it. The zinc is hung on a copper wire, and it is worth making sure that it is placed in the container as conveniently as possible.

In order to connect the device to the power supply, copper wires are used, while the “minus” must be connected to the product, and the “plus” to the zinc electrode. Galvanizing time at home using this method takes from 10 to 40 minutes.

Safety precautions and protective equipment

When planning to begin the galvanizing process using the electrochemical method, it is worth remembering that the electrolyte is a dangerous poison, so the work must be carried out extremely carefully, wearing protective clothing. The room in which metal galvanizing work is carried out must be well ventilated, and the utensils must be made of glass or vinyl plastic

As you can see, galvanizing metal at home is quite simple. The most important thing in this process is to take precautions when handling the electrolytic solution and know the basic rules of the method used.

Source: https://accorel.ru/pokraska/otsinkovka-kak-sposob-zashhitit-metall

How to weld galvanized steel

A zinc coating with a thickness of 2 to 150 microns is applied to rolled steel to protect against corrosive oxidation. With this coating, a film of zinc oxide is formed on the surface of the metal, which protects the steel from the external environment. The crystalline structure of this film is very dense, containing a minimal number of pores, which ensures reliable protection of the metal.

It is necessary to distinguish galvanized steel from “stainless steel”. The zinc coating protects only the top layer of steel, it is inexpensive and therefore galvanized steel is on average 10-20% more expensive than regular steel. Stainless steel is a steel with a high content of alloying elements that prevent corrosion throughout its entire thickness, and the cost of such steel is 5-10 times higher than rolled steel of similar dimensions.

Since galvanized metal in its cross-section consists almost entirely of ordinary steel, the technological process of galvanizing welding differs only in certain features.

Welding of corrugated roofing structures is regulated by departmental standards VSN 349-87. Welding of galvanized metal is carried out in accordance with GOST 5264-80 and 11534-75, which establish requirements for the geometric parameters of joints. There are no separate standards for welding galvanized parts, but departments and enterprises can develop their own regulatory requirements and technical conditions for performing such work.

Preparation

Welding galvanized steel is a job that can be done even by amateur welders. Before carrying out work, it is recommended to practice on some similar scraps in order to “get your hands on” and adjust the settings of the device.

The welder must observe a number of personal safety measures:

• work must be done in a regular protective mask and respirator, or in a mask with a ventilation device;
• Insulated gloves must have a rubber coating.

Galvanization welding is carried out using any of the main joining methods:

1. Manual welding – for steel with a thickness of 1.5 mm.
2. Welding with a semi-automatic machine - used for metal more than 0.6 mm thick.
3. Resistance spot welding – intended primarily for joining sheet metal up to 0.45 mm thick.
4. Gas welding with an oxygen-acetylene mixture – suitable for steel of any thickness.

Regardless of the welding method chosen, a number of conditions must be taken into account:

• The melting point of zinc (420°C) is lower than the melting point of steel (1100-1200°C), and evaporation occurs already at a temperature of 906°C. Zinc vapor in the air pollutes the atmosphere and has a harmful effect on the health of the welder.
• The zinc melt foams and enters the steel structure, violating the specified parameters of the metal, and zinc flowing into the weld leads to a loss of its quality.
• The seam is made “in flow”, the electrode or torch is applied repeatedly, with short touches.
• You should not weld large areas with one seam; you should control the quality of the weld.
• Before welding, the zinc must burn out completely to avoid foaming of the seam.
• When the steel thickness is more than 4 mm, a chamfer is made in the welded joint to 1/3 of the sheet thickness.
• To prevent the zinc from burning out, you can put an asbestos cloth on the metal, or just a wet cloth.

Removing the coating

The first technological operation during galvanizing welding work is the removal of the zinc coating.

The fastest way to clean metal is to heat the part with a gas torch. However, this method is not safe, since zinc is released in the form of toxic fumes.

For small volumes of welding in a workshop, the zinc coating is removed mechanically - with sandpaper, a file, or a grinding wheel on an angle grinder. Heat or acid cleaning can be used, but these methods lead to the formation of harmful fumes.

For large volumes of welding work, galvanizing can be etched using acid. But working with acid requires increased fire safety measures.

When welding galvanized pipes, the zinc coating is removed from both the external and internal sides of the joint, and then the surface is degreased using an acid or alkaline solution.

Inverter Application

It is advisable to use a manual electric arc welding machine to weld steel with a thickness of at least 1.5 mm. Thinner metal is easily burned through and requires some skill during operation and sensitive adjustment of the device. Welding is carried out with reverse polarity of the current, in which a “minus” terminal is attached to the part, and a “plus” terminal is attached to the holder.

The weld welding speed should be less than when welding steel of the same thickness. This reduction must be no less than 10% and no more than 20%. The current strength differs:

• If welding is performed with conventional electrodes OZS-4, UONI-13/45 and 13/55, MP-3, then the current strength should be 5-10A less than for non-galvanized steel.
• If welding is performed with galvanizing electrodes TsU-5, TsL-20, TsL-39 and others, then the current strength is set to 10-50A more, and the gap between the elements being welded should be larger than when connecting non-galvanized steel of the same thickness.

The electrode is tilted to the workpiece no more than 45°, otherwise burning of the metal may occur. The inverter requires careful adjustment of the current and stable voltage, since at low current the seam will not be welded, and too high a current will also lead to through burning of the joint and evaporation of zinc over a large surface area. When there are power fluctuations, the electrode may stick to the metal and damage the integrity of the seam.

The choice of electrode brand should be made taking into account the requirements for the seam joint:

• Rutile-coated electrodes provide a stronger connection, but the seam will require additional anti-corrosion treatment.
• Electrodes containing strong basic fluxes effectively seal the seam, providing it with reliable protection against corrosion, but the strength of the seam will be reduced by 15-25%.

An approximate mode of application of electrodes is presented in the table.

The greatest difficulty in manual welding is the correct regulation of the current and the time of contact of the electrode with the surface.

Using a semi-automatic machine

On many semi-automatic machines there is a “Synergic” welding mode, in which in the settings you can select a specific type of work (preset), most optimally suited for the desired type of metal. If such a mode is not available, additional time will be required to set up the device and, possibly, experiment with welding some trim.

Welding on semi-automatic machines can be carried out either using additives supplied along the hose, or argon can be used as a protective medium.

The wire is selected depending on the thickness of the parts.

If the network voltage is less than 220V, the wire diameter is reduced by 0.2 mm from the recommended one.

The burner is tilted at an angle of 70-75º to the joint surface when making a remelting seam and 20-30º when making a filling seam. In this case, the solder (additive) must be placed in front of the flame so that it does not burn the metal coating.

The use of copper-based filler materials allows you to create a shielding gas environment in the welding area. This technology has a number of advantages:

• the welding seam and the metal surface around it are protected from corrosion;
• minimal melt spattering;
• flux consumes a significant amount of heat generated, thus preventing heating of a large area of ​​metal;
• subsequently the seam can be easily processed.

The melting point of copper additives is lower than that of steel, so this type of welding is more like soldering metal, but ensuring a strong connection. Note that this method avoids damage to the zinc layer.

Depending on the content of these additives, the additives set the desired qualities of the weld:

• The silicon additive CuSi3 makes it easy to process the weld, but reduces its strength properties, since silicon has high fluidity.
• The aluminum additive CuAl8 is used for galvanized steels with a high content of this alloying element.
• Silicon-manganese additive CuSi2Mn is intended for creating joints with increased strength.

When welding pipelines with drinking water, fluxes of the HLS-B brand are used, which are safe for health and quickly dissolve in water. When heated, the flux first turns white and then transparent, indicating that it is ready to begin the soldering process.

Metals up to 4mm thick can be soldered in one pass, but larger thicknesses require multiple passes. After welding, solder residues are removed using a brush and water. The inside of the pipe is filled with water for a day, after which it is washed.

contact welding

Spot welding can be done on metal of any thickness, but it is best done on sheet metal, since very thin galvanized sheets are difficult to join using other methods. For welding galvanized steels using resistance welding machines, electrodes of the BrKh and BrKhTsr brands, made on a bronze basis, are used.

Spot welding machines can operate on direct or alternating current, and specialized equipment for welding sheet metal and galvanizing, in addition, has three additional pulse supply modes:

1. preheating of the connection area;
2. welding process;
3. final heat treatment.

The strength of the weld with this method of connection is higher than that of the elements being connected themselves, therefore this type of welding is common when connecting elements of automobile bodies.

It should also be noted that resistance welding ensures uniform welding of the seam along its entire length, which is difficult to achieve with manual welding. Therefore, it is advisable to install a contact apparatus in workshops that regularly weld galvanized products in large volumes.

When spot welding sheets with a thickness of over 1.5 mm, forging is recommended. Forging is an impact on the seam during the cooling process, which is performed with a hammer or sledgehammer.

A significant disadvantage of spot welding is the high energy consumption of welding machines.

Shutdown

After welding work, it is necessary to ventilate the room and remove zinc shavings.

It should be borne in mind that the cleaned areas will be subject to corrosion and cause a decrease in the quality of the entire structure. Therefore, after completing work, it is necessary to remove scale from them, sand the seam and apply a protective coating.

The surface in the area of ​​the weld must be coated with paint or an anti-corrosion coating. A good option would be paint containing 94% zinc dust. It is possible to fuse zinc wire or rods made of zinc-cadmium alloy.

Source: https://svarkoy.ru/teoriya/svarka-ocinkovannoj-stali.html

Chemicals for galvanizing fasteners, hardware and parts

Chemical components of this category are widely used for galvanizing fasteners, hardware and parts. Products that have undergone the galvanizing process have increased resistance to corrosion, mechanical deformation and external influences. Galvanizing allows for further welding of products, which is convenient when installing complex structures. To increase corrosion resistance, the zinc coating is chromated and phosphated. Chromating simultaneously improves the decorative appearance of the coating.

Chemistry for electroplating. Electrolytic galvanizing method

With the electrolytic galvanizing method, zinc coatings are applied to the surface of products in electrolyte solutions under the influence of electric current. The main components of these electrolytes are zinc salts. The essence of electrode processes during electrolytic galvanizing is the occurrence of oxidation reactions (at the anode) and reduction (at the cathode of the product), accompanied by the flow of electrons through the external circuit and the movement of zinc ions in the electrolyte from the anode to the cathode.

Application area

Electrolytic galvanizing is carried out to impart certain properties to metal products: anti-corrosion, protective and decorative, decorative, anti-friction (to impart hardness, wear resistance).

• Transport
• Construction
• Industrial facilities
• Repair of industrial facilities
• Hydraulic structures
• City objects
• Oil and gas industry

Alkaline zinc-nickel coating chemistry RZN-202 series
(cyanide free)

Chemical composition: Zinc ions: 7-12 g/l Sodium hydroxide: 100-140 g/l Additive RZN-202MU: 90 ml/l Additive RZN-202A: 18 ml/l Additive RZN-202B: 15 ml/l Additive RZN -202N: 30 ml / l Galvanizing is carried out at a temperature of 28±2 ℃ at a cathodic current density of 1.5-3.5 A / dm2 and an anodic current density of 15 A / dm2.

Specification: the technology is environmentally friendly in terms of toxicity level and does not harm the environment. The coating is uniform, bright, and has high corrosion and thermal resistance. nickel 12-15%. The chemical component has good dispersion properties and provides the possibility of galvanizing at high current densities.

Chemicals for acid coating of zinc-nickel RZN-211 series
(for electroplating in plating drums and hangers, does not contain cyanide)

Chemical composition: Zinc chloride: 70 g/l Nickel chloride: 140 g/liter Ammonium chloride: 200 g/l RZN-211A active additive: 60 ml/l RZN-211B shine-forming additive: 30 ml/l RZN-211D reagent: 50 ml/lZinc coating is carried out at a temperature of 32-36 ℃ at a cathodic current density of 2-5 A / dm2, anode (nickel-zinc) current density of 1: 2.5-3 A / dm2 and PH 5.0 ± 0.2.

Specification: the technology is environmentally friendly in terms of toxicity level and does not harm the environment. The coating is uniform, smooth, bright white, and has high corrosion and thermal resistance. nickel 8-12%. The chemical component is easy to use, provides a high rate of zinc electrodeposition and the possibility of galvanizing at high current density. The electrolyte is ideal for galvanizing high-carbon steel, cast iron products in galvanic drums and on hangers.

Shine-forming additive for acid galvanizing RZN-28
(for electrodeposition in galvanic drums and on hangers)

Chemical composition:	Galvanizing on hangers	Galvanizing in drums	Specification: durable glossy coating, bright white. The brightening additive is ideal for galvanizing products in galvanic drums and on hangers. The use of the component does not cause difficulties in wastewater treatment. Adjustment of the solution: Shine-forming additive RZN-28: 150-200 ml / KAH Softening additive RZN-30: as needed.
Zinc chloride	60-80 g/liter	40-60 g/liter
Potassium (sodium) chloride	180-220 g/liter	180-220 g/liter
Boric acid	25-35 g/l	25-35 g/l
Shine additive RZN-28	0.5-1.0 ml/l	0.5-1.0 ml/l
Softening additive RZN-30	20 ml/l	20 ml/l
Galvanizing is carried out at a temperature of 15-50 ℃ at a cathode current density of 0.5-3.5 A / dm2 (on hangers), 0.1-1.0 A / dm2 (in drums) and PH 4.5-5.5.

Alkaline galvanizing additive for RZN-H100 series
(cyanide-free)

Chemical composition: Zinc oxide: 7-15 g/l Sodium hydroxide: 70-150 g/l RZN-H100A active additive: 4-6 ml/l RZN-H100B shine additive: 4-6 ml/l Solution adjustment: RZN- H100A active additive: 100 ml / KAHRZN-H100B shine additive: 100 ml / KAH

Specification: the coating is uniform, bright glossy. The chemical component has good dispersion properties, is stable, easy to operate, and provides the possibility of galvanizing at high current densities. The absence of cyanide does not require the use of additional efforts in wastewater treatment. Galvanizing is carried out at a temperature of 20-40 ℃ at a cathode current density of 0.5-6.0 A / dm2.

Shine-forming cyanide additive for galvanizing series RZN-22
(for electrodeposition in galvanic drums and on hangers, contains cyanide)

Chemical composition: Zinc oxide: 10-20 g/l Sodium hydroxide: 70-100 g/l Sodium cyanide: 10-50 g/l Shine additive ZN-22: 4-6 ml/l Solution adjustment: Shine additive RZN-22 : 100-150 ml/KAH

Specification: the coating is uniform, bright. The brightening additive is simple and economical to use, ideal for galvanizing products in galvanizing drums and on hangers. Galvanizing is carried out at a temperature of 20-40 ℃ at a cathode current density of 0.5-6.0 A / dm2.

Technology and methods of galvanic galvanizing

Galvanizing is the main way to protect the base metal of hardware from corrosion. As a rule, protection by this method is used for various grades of carbon and alloy steels. Galvanic galvanizing in hardware production is used to protect wire products and various fasteners from corrosion. The zinc coating significantly increases the service life of the product and reduces the costs of its maintenance and replacement.

The principle of protecting products based on zinc coating is determined by the difference in the electrochemical potentials of Zn and Fe. The zinc coating acts as an anode in a humid environment, taking on all the harmful processes of oxidation reactions and thereby protecting the base metal of the product.

The inexpensive galvanizing process and the high degree of anodic protection of the base metal have made this technology the most popular for corrosion protection in the production of hardware.

Electrolytic galvanizing technology is a chemical process - electrolysis.

In the electrolyte bath there are two metals, steel products and pure zinc. Electric current is supplied to them. Steel products are loaded into a container, and current is supplied to them through special electrodes. Zinc can be used in the form of plates, balls loaded into special mesh sections, or in other forms. Current is also supplied to the zinc.

During the electrolysis process, zinc (anode) dissolves and its ions settle on the surface of steel products, forming a galvanic coating with a thickness of 4 to 20 microns. Anodic dissolution of zinc electrodes occurs as a result of passing an electric current through the electrolyte with a cathode density of 1 to 5 A/dm2.

With this technology of applying zinc coating, a uniform, shiny coating is obtained.

Galvanizing methods

Currently, in hardware production, three methods of galvanic galvanizing are used to protect products from corrosion: cyanide, alkaline and acid.

Cyanide method

The cyanide method is the most highly toxic due to the presence of sodium cyanide, as well as sodium hydroxide and zinc oxide in the electrolyte. By changing the percentage of components, you can give different properties to the electrolyte.

The positive aspects of cyanide electrolytes are the high productivity of electroplating lines, good covering ability, which allows processing parts of complex shapes, the durability of the electrolyte and the ease of its adjustment.

The disadvantages of this galvanic galvanizing technology include a high degree of environmental hazard and hydrogen embrittlement acquired by galvanized carbon steel products. Hydrogen embrittlement is the most significant disadvantage, especially for high-strength fasteners, significantly reducing their static and fatigue strength.

Alkaline method

An alternative to cyanide electrolyte can be alkaline electrolytes, which contain 1-2 g of zinc oxide and 10-20 g of sodium hydroxide per 1 liter of solution. Such electrolytes are less hazardous to the environment than cyanide ones, but they are not without significant drawbacks. Alkaline electrolytes are recommended for use only for processing steel; The galvanizing process stops when the electrolyte is heated to more than +30°C.

Just as with the cyanide galvanizing method, significant hydrogenation of the processed products occurs, which does not allow the use of this galvanizing method to protect high-strength fasteners from corrosion. When using modern alkaline galvanizing technologies, coatings have a high degree of decorativeness.

The use of various passivators allows you to give the coating any color - from white with a bluish tint to dark olive green and even black.

Acid method

The most popular galvanizing technology is galvanizing technology in weakly acidic electrolytes. This technology has a high degree of concealment and improved appearance of the zinc coating.

This method, in addition, reduces the tendency of galvanized products made from carbon and alloy steels to hydrogen embrittlement and makes it possible to galvanize parts of complex configurations made of both steel and cast iron. In modern hardware production, this method of applying a protective coating is the most common among fastener manufacturers.

Galvanizing in slightly acidic electrolytes allows you to obtain the greatest decorative effect. Products with a protective zinc coating, obtained using low-acid galvanizing technology, have high gloss, a variety of colors and high corrosion protection.

Surface preparation

All galvanic technologies require high quality preparation of the surface of the processed products. Before the galvanizing process, it is necessary to clean the surface from scale, process lubricant residues, and corrosion products (rust). After applying the zinc coating, for greater stability and durability, the coating is subjected to clarification (decapitation - etching in a weak solution with nitric acid) and passivation.

Passivation gives the zinc coating not only additional corrosion resistance, but also improves its decorative effect by adding additional shine or painting the coating in different colors. Most passivation solutions contained Cr 6+ ions as the most effective and cheapest way to additionally protect the zinc coating.

However, since 2007, the use of Cr 6+ has been prohibited in the EU, and manufacturers have switched to less dangerous passivators based on Cr 3+ and to new types of effective chromium-free protective coatings.

Source: https://www.metiz.com.tw/chemicals_zinc.htm

What does zinc coating do for metals?

We often hear and see in advertising that if we are to protect metals from corrosion, then only with the help of zinc. But not everyone knows why zinc? We will tell you in this article what zinc coating does for metals.
 

Galvanizing is the most effective method of protection

Galvanizing is the coating of various metal surfaces with a layer of zinc to protect against corrosion. The fact that galvanizing is the most effective method in the fight against rust was discovered a long time ago, more than 200 years ago. When conducting research on various methods, it was galvanizing that showed the most long-term results - for more than 50 years, metals coated with a layer of zinc do not rust.

Since then, anti-corrosion specialists have used galvanizing in various ways. Initially it was hot-dip galvanizing, then galvanic, diffusion, gas-dynamic. But in the 80s of the 20th century there was a certain breakthrough in this area, a new method appeared - cold galvanizing.

Cold galvanizing is the most convenient, economical and durable method of applying zinc coating. It consists of coating the prepared metal surface with a composition with a very high (96-98%) zinc content, as well as various additives.

The cold galvanizing composition can be applied using a regular brush or roller, right at the site where the structure is used, that is, it does not need to be transported anywhere.

The result of such protection is the absence of corrosion for 25-50 years, and metals protected by cold galvanizing corrode 3 times slower than those protected by other methods, despite the same zinc in the composition (according to studies by the Fulmer Center). What's the secret?
 

How does zinc coating work?

Iron, when interacting with moisture and oxygen, oxidizes and forms a fragile, loose film on the surface, which gradually turns into rust. Such unreliable protection continues to allow moisture and oxygen to penetrate deep into the iron and destroy it. But zinc, tin and aluminum, when interacting with moisture and oxygen, form a durable film that prevents further destruction. That is why a thin layer of these metals is used to protect other metals that are more susceptible to corrosion.  

Zinc stands out among this group of “durable” metals in that it provides further protection from moisture and oxygen even if the coating is damaged, while the protection of tin or aluminum weakens or even begins to promote corrosion if the integrity of the layer is compromised.

Zinc protects metals in two ways at once - barrier (passive) and cathodic (also called active, sacrificial or electrochemical). 

Cathodic protection implies that zinc, when applied to iron, forms a galvanic couple with it, in which iron is a less active metal and zinc is a more active one. When in contact with moisture and oxygen, the zinc anode reacts first, donating its electrons to fight corrosion, and the iron cathode accepts electrons, is protected and remains practically untouched by rust. The protective process continues until the zinc layer is completely depleted. 1 layer of 40-60 microns is enough for 10-25 years.   

Two methods of protection at once, which replace each other, are very useful for metals from the first day of operation. The fact is that any coating with the composition is not 100% airtight, but has defects and pores. The zinc coating may also allow some oxygen to pass through during initial use.

 It is then that it protects metals from rust using a protective or electrochemical method. During operation, the coating structure becomes compacted, the zinc compounds are completely dissolved, and barrier protection takes effect, as with hot-dip galvanizing.

If the integrity of the coating is compromised (scratches, mechanical damage, corrosion by chemicals), then cathodic protection will take over the job again. 
 

Not just zinc - or why does cold galvanizing protect longer?

In practice, zinc coating is the most reliable and durable. However, one zinc coating is different to another. You can buy paint with zinc and apply it correctly, but the protection will not last for decades. Because zinc added to paint will not work in this way. Such long-term protection (25-50 years) is provided only by cold galvanizing compounds. Why is cold galvanizing more durable than other zinc processing methods?

Cold galvanizing provides the same protective characteristics as other methods such as hot galvanizing. But, unlike them, it is much easier to apply on site where structures are used, costs less and lasts longer.

Cold galvanizing compositions contain 96% or more zinc, with a purity of 99.995%. That is, almost 100% without impurities! And the higher the concentration of zinc and its purity, the longer the coating will last. This is what allows the “cold” coating to corrode as slowly as possible, compared to other galvanizing methods.

 The zinc particles in the composition are protected by resins - this further increases the protective characteristics of the coating. In addition, the minimum particle size (from 12-15 microns, to 3-5 microns in different compositions) and their oval shape form a strong electrochemical connection with the metal. Thanks to this, even scratches and damage to the surface of the coating do not lead to peeling, maintaining excellent adhesion.

Only active coatings with cathodic protection can do this. But simply coatings in which zinc is added cannot do that.  

Even such a proven method of galvanizing as hot galvanizing is slightly inferior to cold galvanizing. Because during hot-dip galvanizing, compositions with a zinc content of 80-85% with a purity of up to 98% are used. There are no resins that protect zinc, since they will not withstand heating up to 400°C and will still lose their protective properties. In addition, not every structure can be disassembled, transported and placed in a hot zinc bath.
 

How long will cold applied zinc protection last?

The service life of coatings applied by cold galvanizing differs depending on operating conditions and layer thickness, as well as the degree of cleaning of the metal surface. A polluted atmosphere, the influence of various chemicals, gasoline, salts, alkalis and petroleum products can slightly accelerate the depletion of the coating. The lifespan of coatings used outdoors is always shorter than more careful indoor use.

Terms guaranteed by the manufacturer for the cold galvanizing composition Barrier-zinc:

Dependence of layer thickness and service life of Barrier-zinc coating:

• 40 microns: 7-10 years;
• 60 microns: 10-20 years;
• 80 microns: 14-25 years;
• 100 microns: 18-25 years;
• 120 microns: more than 20 years.

It is worth noting that these are the terms guaranteed by the manufacturer. The actual service life of the coating is 1.5-2.5 times longer than the warranty period. In addition, the service life of such a coating can always be extended at any time by adding another layer and making it thicker.

Our website also presents other zinc-containing primers that provide reliable and durable protection of metal from corrosion. For example, Barrier-Grunt is a one-component anti-corrosion primer with zinc to protect metal in various environments (soil, water, atmosphere).
 

Have questions about choosing a composition? Contact the representative office in your city:

in St. Petersburg: (812) 603-41-53, (921) 927-58-47
in other cities: 8 (800) 707-53-17
e-mail: [email protected]

Source: https://terazinc.ru/tsinkovanie_metalla_i_izdeliy/chto_daet_tsinkovoe_pokritie/

How to distinguish galvanized steel

When manufacturing metal containers or structures (for example, the widespread construction of hangars or warehouses), the quality of the metal, and, in particular, its corrosion resistance, is important. For this purpose, steels with protective (usually zinc) coatings, as well as stainless steel and aluminum are widely used. How can you distinguish between these metals and protect yourself from the actions of unscrupulous dealers?

Distinguishing aluminum from galvanization

In order to reduce the load on supporting structures, they are often made of aluminum. It is easy to distinguish aluminum from galvanized steel, especially if the buyer is not presented with a finished assembly, but with blanks made from rolled sheets or profiles. Main methods:

• By density/weight. The density of aluminum (2700 kg/m3) is almost three times less than the density of steel (76007900 kg/m3).
• In terms of surface hardness, aluminum is softer, and when scratched it will leave a deeper groove on a smooth surface.
• According to the effect on the tissue organs of the fingers. The thinnest film of aluminum dioxide upon frictional contact with wet skin of the hands will leave particles of aluminum on the surface of the fingers. When you touch them to a sheet of clean paper or cardboard, dark gray stripes will remain on it.

Externally, aluminum looks more silvery than steel, especially hot-rolled steel.

We distinguish between galvanized and non-galvanized steel

Both stainless steel and galvanized steel are characterized by good resistance to corrosion, so for short service life of structures (up to 10 years), the lower price of galvanized steel can be the decisive choice. It’s a different matter if the design is designed for a shorter period of use, and there is a reason to use ordinary steel. In such cases, it may be necessary to distinguish galvanized steel from non-galvanized steel.

A simple test will help you determine the difference between regular and galvanized steel:

• Prepare a solution of three parts table salt (not iodized!) and one part warm water.
• Dip a clean rag/cloth napkin into the solution and wipe the surface of the steel being tested with it.
• We keep the sample for 24 hours in a normal room at room temperature (you can’t leave it in the sun).
• We inspect the sample: if there are no traces of rust on it, and the surface texture is not uniform in the treated and untreated areas, then this is galvanized steel.

The basis of the test is that as a result of galvanic galvanizing - hot or cold - zinc actively penetrates deep into the base metal, introducing itself into its structure, which acquires anti-corrosion resistance. Ordinary steel does not have such a protective coating, so a saturated saline solution activates the oxidation process with the formation of light red iron oxide.

Another way to distinguish galvanized steel from non-galvanized steel is based on the different magnetic properties of the metals. Zinc, for example, is non-magnetic, so by applying a regular magnet to the unpainted surface of a workpiece, you can determine whether it contains zinc or not.

If the surface of the workpiece is already painted with heat-resistant paint, a magnet will not help. Laboratory testing is required. The greatest accuracy will be obtained by testing for electron paramagnetic resonance (EPR). EPR shows the content of material molecules on an oscilloscope, so galvanized steel will have a high zinc content on the outer surface and its presence in the inner layers. When painting, no zinc will be found in the coating.

Another method is to take a microphotograph of a ground cross-section of the sample. When galvanizing, three intermetallic layers are clearly visible in the structure, which are absent in conventional steels.

In conclusion, we will present an exotic method - you just need to lick the steel surface. Galvanized steel, unlike ordinary steel, has a chalky aftertaste, and a very distinct one.

We distinguish between galvanized and stainless steel

It is not easy to visually distinguish stainless steel from galvanized steel, since the difference in density is hardly noticeable (as is the appearance of the metal). The following types of tests must be used:

• For mechanical strength in the original state. Most grades of stainless steel have a tensile strength of at least 450 MPa. For galvanizing, this figure is much lower - up to 300350 MPa.
• For hardness according to Brinell HB. For stainless steel, NV 230300 is considered normal, for galvanized steel – NV 200250.
• For plasticity. The specific force at which cracks appear on the workpiece is 170230 MPa for galvanized steel, and 350400 MPa for stainless steel.

If mechanical tests are not enough, chemical tests are carried out using hydrochloric acid. The method is based on the properties of zinc, which, when interacting with a galvanized sheet coating, actively releases hydrogen. A small drop of hydrochloric acid is enough for the galvanized surface to begin to bubble, and the zinc layer gradually disappears. The surface of stainless steel is chemically inactive.

Electromagnetic differences between galvanized and stainless steel can also be used for evaluation. If a magnet is attracted to the workpiece, then with a high degree of certainty we can say that it is galvanized steel, while most stainless steels are non-magnetic.

Source: http://www.hugebuilding.ru/otlichiya-ocinkovki.html