Do-it-yourself soldering acid: composition and purpose, do-it-yourself production - Machine
Soldering acid is a flux that can be classified as a separate category, because it has an aggressive effect on materials that are needed during work. This flux mainly spreads in a liquid state, and this does not depend on its concentration. Sometimes you can purchase a concentrated substance and then dilute it, or perhaps buy a ready-made, diluted one. In addition, everyone can easily make soldering acid on their own.
The properties of materials must be selected according to those factors that are necessary for their use.
Soldering acid is intended for those metals that are heavily contaminated, because oxidation occurs on them, and a large amount of rust remains on the surface.
The material is very active, so it is necessary to work with it carefully and avoid contact with human skin and mucous membranes. You must first carefully familiarize yourself with the rules and methods of using acid, and only then begin to use it for its intended purpose.
In the process of producing soldering acid yourself, it is necessary to use special technology. In the end, the result should be a material that will have the properties prescribed by GOST. This is what will make the flux high-quality and reliable so that the connections are strong.
It is necessary to ensure that the properties and functions of the acid work even after soldering the metals, because the material removes films and rust from the surface, and also prevents their reappearance.
You should also take into account the spreadability of the materials being soldered over the surface and the adhesion to metals and products.
Characteristics, composition and properties
It is necessary to know exactly what the material should consist of, and only then begin its production. Soldering acid includes:
- wetting additive;
- ammonium chloride;
- deionized water;
- zinc chloride;
- hydrochloric acid.
Soldering acid, created independently, may consist of other components. You just need to do everything to ensure that the flux has all the necessary properties. It is necessary to ensure high activity of this material.
It must interact with the necessary materials in a minimum amount of time, and also destroy all substances that prevent normal soldering. However, it is worth considering that small parts may be damaged and deteriorated when exposed to acid.
Solder active fat has the same properties.
The acid has a rather unpleasant odor, so when a person inhales it, his health may suffer. That is why it is recommended to use a respirator when working with this material.
Well, the work area must be constantly ventilated.
It is necessary to protect your hands, skin and mucous membranes from acid; it is necessary that the workpiece gets only into the places necessary for soldering.
Materials and tools for making acid
You need to know that the soldering acid you make yourself will have a slightly different composition than the purchased one. However, it will be simpler. To prepare such acid, you need to use some equipment:
- Glass container or jar for mixing and preparing the material.
- Zinc granules or cups from used batteries containing this element.
- Tap clean water.
- Concentrated hydrochloric acid, which is capable of dissolving unnecessary impurities and substances.
Making acid yourself
First you need to take a container or jar for mixing the acid. This is where the zinc or batteries and their remains are placed.
Only after all of the above can hydrochloric acid be poured into the container. The main thing is to act with great caution, because if it comes into contact with the skin, you can get a serious burn.
The acid in the container should not be more than 3/4 of the volume of the entire composition.
As a result, it turns out that the proportions should be like this. For 1 liter of hydrochloric acid, 412 grams of zinc are needed, but this can only be measured using special tools. Therefore, it is worth knowing that there will be some deviations in one direction or another.
When further preparing soldering acid, you must wait for the reaction of the chemicals to finish. Zinc and acid come into contact with each other, the metal gradually dissolves. During this process, active hydrogen evolution occurs, so many bubbles can be seen in the liquid.
The liquid gradually becomes clearer and cleaner. When all processes are completed, it is necessary to pour the liquid into a tightly closed container. All these materials can be easily purchased in stores specializing in the sale of chemicals and reagents. When using batteries, you can see that almost any of them will do.
If you need to make a material with weaker properties, then you should slightly reduce the aggressiveness. In this case, it is recommended to add a little water to make the solution more liquid and with weaker properties.
However, you need to be careful, because the liquid can splash and get on the skin and mucous membranes of a person.
In this case, you should choose the proportions yourself, adhering to the specifics of the required soldering.
Making soldering acid yourself
First, you should take care of your own safety, because using acid is very dangerous and can cause irreparable harm to your health. If acid production is carried out in enterprises and industrial areas, then everything must be done in special-purpose cabinets.
The reagents are reliably protected from outsiders, and they are poured strictly under special hoods. At home, it is recommended to use protection, gloves, goggles, respirators and other devices. Dissolving the acid should only be done in a well-ventilated area or even outside.
Indeed, in the process of creating acid for soldering, hydrogen is constantly released into the air in large quantities. It is also necessary to take care, just in case, of water, with which you can quickly rinse the area of skin on which the substance has come into contact.
It is best to use cold tap water because in the event of an accident, it will reduce pain and quickly clean the wound.
If this substance is spilled on the surface, it is best to wash it off with a special mixture of water and alkali.
You must also remember that this material must be stored correctly, the container must be closed and sealed, storage is carried out in a dark and cool place.
It is recommended to prevent unauthorized people from accessing the soldering acid to avoid danger to others. Flux is sometimes made from pure hydrochloric acid without zinc and water. However, it is mostly used only for iron products.
Source: https://regionvtormet.ru/beton/payalnaya-kislota-svoimi-rukami-sostav-i-prednaznachenie-izgotovlenie-svoimi-rukami.html
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Hydrochloric acid (hydrochloric acid) is a solution of hydrogen chloride in water; strong monobasic acid, formula HCl. Synthetic hydrochloric acid is used in the chemical, medical, food industries, non-ferrous and ferrous metallurgy. The product is transported in special rubberized tanks of 42-70 tons, polymer barrels, and containers.
Synthetic hydrochloric acid has a Certificate of Conformity and a Certificate for the use of the product in technological processes of oil production and transportation.
Abgasic hydrochloric acid is used in the chemical industry to acidify brine in the production of caustic soda, to produce regenerated hydrogen chloride, to produce metal chlorides, in ferrous and non-ferrous metallurgy - to remove the oxide film from the surface of the metal, in the process of leaching metal from ores; in other industries - for cleaning boilers and for chemical water treatment not related to drinking water supply.
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Soldering acid recipes
Hydrochloric acid mixed with water and other materials is used to remove scale in the cooling system of automobile engines, to pickle the surface of metal products before tinning and soldering, and to prepare pickled acid by dissolving pure zinc in it.
Their solutions have antiseptic properties. A solution of zinc chloride in hydrochloric acid (etching acid) is used when soldering metals, as it helps remove oxides and hydroxides from the surface of metals.
The mechanism of this process comes down to the formation of complex compounds. The success of soldering is associated with the quality of surface preparation; it should be as well cleaned as possible and with the type of flux used to clean the surface of the product from oxides and to protect it from oxidation during the soldering process. When soldering with normal soft solders, pickled acid and rosin are used as fluxes.
Sometimes a solution of zinc chloride is prepared directly by dissolving zinc in hydrochloric acid. This process is usually called pickling, which is why the zinc chloride solution is sometimes called pickling acid. Then, to clean it, rub it with the sharp end in ammonia or rosin and, without allowing it to cool, touch the solder with the cleaned sharp end, which sticks to it in a small amount.
The end of the soldering iron with the solder stuck to it is passed over the place to be soldered, previously lubricated with etched acid. At this time, the surface to be soldered must be motionless. It is necessary to ensure that the parts to be soldered are pressed tightly against each other. For acid soldering and tinning of parts made of brass, copper, and steel, zinc chloride and etching acid are used, and for acid-free soldering of parts made of copper and brass, rosin or solder fat is used.
When soldering with hard solders, sodium borate or boric acid is used as a flux. A low-melting alloy of lead and tin is still used as solder, and the reducing agent is the so-called etched acid - a solution of zinc chloride in hydrochloric acid. To do this, the bearing is heated to 60 - 70 C, moistened with a solution of hydrochloric acid, wiped and washed with water.
Then the bearing is moistened with etched acid, sprinkled with ammonia powder and ammonium chloride, heated to - C and a thin layer of solder is applied with a solder stick, which should evenly cover the surface and not drain from it.
The tinned surface is wiped with tow and ammonia powder. After tinning, it is immediately filled with babbitt in order to prevent the appearance of oxide films on the half-plate layer.
For tinning, by rubbing the tertiary, the liner on the back side is heated to 60 - 70 C. The surface to be tinning is moistened with hydrochloric acid, wiped, washed with hot water and wiped dry. Then the surface to be tinned is moistened with etched acid HC1, sprinkled with ammonia powder and the liner is heated to - C. A thin layer of molten half-water is applied with a tertiary stick, which should give a smooth, shiny surface.
Zinc chloride is a white powder that easily absorbs moisture. It is stored in a tightly sealed container. An aqueous solution of zinc chloride, obtained by a chemical reaction of zinc with hydrochloric acid (etching acid), is not recommended to be used as a flux for soldering critical parts, since it has increased corrosive activity, but the activity can be reduced by evaporating water and acid residues from the solution.
The next operation is etching the bearing with hydrochloric acid. Etched hydrochloric acid is a percentage aqueous solution of zinc chloride. The purpose of etching bearings before tinning is to remove from them a hard film of oxides that interferes with the adhesion of poluda and babbitt.
Pickled acid is prepared by dissolving zinc metal in hydrochloric acid at the rate of 0.3 kg per 1 kg of acid. The surface of the bearing is coated with acid using a brush dipped in it. After this, there should be no dry places on the surface of the bearing, the presence of which indicates poor cleaning of the surface from fatty substances, as a result of which the half will not stick in these places.
Therefore, if during etching areas are found that are not wetted with the etching acid, they should be cleaned again. Therefore, if during etching areas are found that are not wetted with etching acid, they should be cleaned again.
The old fill is removed by melting it over a calm, even fire. Using sandpaper or a steel brush, thoroughly clean the entire surface of the liner that will be filled with the alloy to a metallic shine. After degreasing, the liner is washed in hot water to remove any remaining alkali. After heating, the surface is lubricated with etched acid and covered with ammonia powder before tinning.
Source: https://all-audio.pro/c33/obsuzhdeniya/kak-travit-solyanuyu-kislotu.php
Acid for rust removal
The most terrible enemy of metal structures is rust, which appears due to the interaction of oxygen with water. There are quite a few different ways to remove corrosion from a metal surface, but hydrochloric acid is the most effective for removing rust. It can be used in its pure form or as a main component of modern chemical compositions to eliminate corrosion.
There are several basic methods for cleaning metal structures from rust stains, based on the degree of the corrosion process:
- submersible, immersing the part in the solution;
- one-time or repeated manual treatment of products with hydrochloric acid;
- carrying out metal processing with preliminary mechanical cleaning.
What is hydrochloric acid
Hydrochloric acid is a water-soluble product of inorganic origin. This substance looks like yellow syrup.
Hydrochloric acid has a variety of uses, but it is most popular as a remedy for removing rust stains. Using hydrochloric acid, you can not only clean loose rust, but also obtain an oil-type protective film.
After the acid eats away the rust, a protective layer appears on the surface.
Advantages of hydrochloric acid:
- removing rust deposits from the surface of metal structures, as well as on enamel and earthenware;
- gentle removal of corrosion without damaging surfaces;
- creating a protective coating on the surface of structures to prevent further corrosion;
- cleaning plaque and dirt from plumbing fixtures.
Features of professional rust removers based on hydrochloric acid
Chemical rust removers are manufactured to clean corrosion from different types of metal structures. Rust stain removers are professional products with a high level of concentration, which must be proportionally diluted with water in the ratio recommended by the manufacturer (1:3).
It is first necessary to test the effect of the chemical on a small area of the metal structure in order to select the optimal ratio of the active substance and water, focusing on the depth and amount of destruction. When the remover is exposed to water and air, it does not release toxins.
The product is explosion-proof and fireproof.
Basic safety requirements when working with acids
When removing rust with acidic compounds, you must adhere to the safety requirements and recommendations of the manufacturer of the chemical composition. All procedures must be carried out exclusively in special gloves made of thick rubber, construction safety glasses, a mask and a change of clothes.
If there is no special clothing for the work, you can cover your clothes with an apron. If acid gets on your skin or eyes, you should rinse the affected area with plenty of running water as quickly as possible.
If pain and discomfort bother you for a long time, you need to seek help from a medical clinic.
Source: https://syntilor.ru/udalitel-rzhavchiny/kislota-dlya-udaleniya-rzhavchiny/
How to remove zinc coating from metal?
Galvanizing is recognized throughout the world as the most effective way to protect metal structures, pipes, wires, bolts, nuts and other hardware products from the negative effects of the environment. Due to the relative cheapness of galvanizing technology, prices for galvanized products are much lower than prices for stainless steel hardware. But if you need to connect the elements by welding, then the zinc coating can become a serious problem.
Features of welding galvanized metal
The need to remove zinc coatings from metals usually arises during welding operations. Every welder knows that welding galvanized surfaces is problematic and even the thinnest layer of zinc can greatly deteriorate the strength properties of the weld.
An admixture of zinc that gets into the weld pool leads to pore formation and the appearance of crystallization cracks in the seam, that is, it does not allow a dense and uniform seam to be obtained.
In addition, during welding, zinc begins to evaporate under the influence of a high-temperature arc, and its toxic fumes can cause severe poisoning and even suffocation of the welder, especially when working in a poorly ventilated area.
Methods for removing zinc from welded surfaces
Mechanical. Unwanted zinc coating can be removed from metal surfaces using an abrasive grinding wheel. Sometimes it is enough to clean the part to a metallic shine with a brush with stiff wire bristles (cord brush).
Thermal. An effective way to remove metal coating is to burn off the zinc with a high-temperature flame, such as using a torch. At the same time, you should remember the toxicity of zinc and take all safety measures.
Chemical. When welding critical structures, it is better to pre-clean surfaces from zinc in a weak solution of hydrochloric acid (5%). Zinc is more active than steel, so it reacts effectively with acid and is easily removed from hardware. To prevent acid corrosion of steel, 1% methenamine can be added to the solution.
The part to be welded is immersed in a bath of dilute acid at room temperature. The cleaning process (etching) lasts several minutes.
When it is complete, and this will be evident from the attenuation of the hissing, the metal is treated with an alkali to neutralize the acid, for example, a soda solution (1g / 50ml), then washed with water and dried until the moisture has completely evaporated.
For chemical etching of galvanized parts being welded, many welders use a proven and effective product - spent acid battery electrolyte, which is nothing more than an aqueous solution of sulfuric acid. Just a few minutes in such a bath and not a trace will remain of the zinc coating on the metal.
Useful tips 09.20.2019 12:51:11
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Source: https://Krepcom.ru/blog/poleznye-sovety/kak-udalit-tsinkovoe-pokrytie-s-metalla/
About hydrochloric acid
Hydrochloric acid is a clear, colorless or yellowish liquid without suspended or emulsified particles.
Hydrochloric acid is a solution of hydrogen chloride gas HCl in water. The latter is a hygroscopic, colorless gas with a pungent odor. Typically used concentrated hydrochloric acid contains 36–38% hydrogen chloride and has a density of 1.19 g/cm3.
Such an acid smokes in air because gaseous HCl is released from it; When combined with air moisture, tiny droplets of hydrochloric acid are formed. It is a strong acid and reacts vigorously with most metals. However, metals such as gold, platinum, silver, tungsten and lead are practically not etched by hydrochloric acid.
Many base metals, when dissolved in acid, form chlorides, for example zinc:
Zn + 2HCl = ZnCl2 + H2
Pure acid is colorless, but technical acid has a yellowish tint caused by traces of compounds of iron, chlorine and other elements (FeCl3). Dilute acid containing 10% or less hydrogen chloride is often used. Dilute solutions do not emit HCl gas and do not smoke in either dry or humid air.
Application of hydrochloric acid
Hydrochloric acid is widely used in industry for extracting metals from ores, pickling metals, etc. It is also used in the manufacture of soldering fluid, in the deposition of silver, and as a component of aqua regia.
The scale of use of hydrochloric acid in industry is less than that of nitric acid. This is due to the fact that hydrochloric acid causes corrosion of steel equipment. In addition, its volatile vapors are quite harmful and also cause corrosion of metal products.
This must be taken into account when storing hydrochloric acid. Hydrochloric acid is stored and transported in rubberized tanks and barrels, i.e.
in vessels whose inner surface is coated with acid-resistant rubber, as well as in glass bottles and polyethylene containers.
Hydrochloric acid is used to produce chlorides of zinc, manganese, iron and other metals, as well as ammonium chloride. Hydrochloric acid is used to clean the surfaces of metals, vessels, and wells from carbonates, oxides and other sediments and contaminants. In this case, special additives are used - inhibitors, which protect the metal from dissolution and corrosion, but do not delay the dissolution of oxides, carbonates and other similar compounds.
HCl is used in the industrial production of synthetic resins and rubbers. It is used as a raw material in the production of methyl chloride from methyl alcohol, ethyl chloride from ethylene, vinyl chloride from acetylene.
Hydrochloric acid poisoning
HCl is poisonous. Poisoning usually occurs through fog formed when gas interacts with water vapor in the air. HCl is also absorbed on the mucous membranes with the formation of acid, causing severe irritation.
When working for a long time in an HCl atmosphere, catarrh of the respiratory tract, tooth decay, ulceration of the nasal mucosa, and gastrointestinal disorders are observed. The permissible content of HCl in the air of working premises is no more than 0.005 mg/l.
For protection, use a gas mask, safety glasses, rubber gloves, shoes, and an apron.
At the same time, our digestion is impossible without hydrochloric acid; its concentration in gastric juice is quite high. If the acidity in the body is low, then digestion is impaired, and doctors prescribe such patients to take hydrochloric acid before eating.
Household use of hydrochloric acid
Concentrated “hodgepodge” is mixed with water in any proportion for household needs. A strong solution of this inorganic acid can easily clean earthenware plumbing fixtures from limescale and rust, while a weaker solution can remove stains of rust, ink, and berry juice from fabrics.
If you look closely, the “Toilet Duck” toilet bowl cleaner says that it contains hydrochloric acid, so you need to work with it in rubber gloves and protect your eyes from splashes.
In addition, the life of no one is unthinkable without this acid - it is contained in the stomach and it is thanks to it that food that enters the stomach dissolves (digests).
In addition, this acid serves as the first barrier against pathogenic bacteria that enter the stomach - they die in an acidic environment.
Well, people suffering from gastritis with high acidity are also very familiar with this acid. They even reduce its effect so that it does not destroy the walls of the stomach, using special drugs that interact with it and reduce its concentration.
The most popular are preparations containing magnesium and aluminum oxides, for example, Maalox. However, there are also extreme sports enthusiasts who drink baking soda, although it has already been proven that this only leads to temporary relief.
Source: https://xn--c1acbdje2abnav6d.xn--p1ai/stati_o_kislotah/o-soljanoj-kislote
Hydrochloric acid for sewer cleaning
Hydrochloric acid is a homogeneous, colorless liquid with a pungent odor. It is a very caustic substance that reacts with most metals. Thanks to these properties, the material is widely used not only in industry, but also in everyday life.
The reagent is included in various means for getting rid of sewer blockages, but it can be used for this purpose independently, after diluting it with water in the required proportions.
The use of an acid solution in the home is not limited to this: the material is used to clean plumbing fixtures from rust and limescale, remove stubborn stains from fabrics, and even to remove scale from a kettle.
Precautionary measures
Since the reagent has a strong corrosive ability and releases toxic fumes when interacting with air, it is very important to use protective equipment when working with it.
When contacted with the skin and mucous membranes, the material causes chemical burns, and with prolonged exposure to an HCl atmosphere, tooth decay occurs, catarrh of the respiratory tract develops, and ulceration of the nasal mucosa occurs.
For protection purposes, it is necessary to use a gas mask, a rubberized apron, goggles and rubber gloves. Carry out work only in well-ventilated areas. If the reagent gets on your skin or mucous membranes, rinse the affected area with plenty of running water and seek medical help.
How to get rid of blockages?
For tough and targeted cleaning of sewers from organic deposits (fats, food debris, hair, detergents, etc.), dilute hydrochloric acid should be used. This method is not suitable for steel, iron and plastic pipes, since the connection can lead to corrosion and even the formation of through holes.
Before starting the procedure, you need to close the drain holes in other plumbing fixtures and ensure air flow into the room. This step is necessary, since during operation the acid will begin to actively produce toxic gases.
It is recommended to dilute the composition with water until a concentration of 3-10% is reached, then pour directly into the sewer and leave for 1-2 hours. Then you need to rinse the pipes with plenty of water and repeat the procedure if necessary.
Important point! The reagent should not be mixed with other drain cleaners, especially those based on alkalis. Otherwise, the reaction of these connections will cause severe damage to the pipes.
Other uses of acid in everyday life
An acid composition can easily clean faience plumbing from limescale and rust, remove urinary stone and other contaminants. For greater effect, an inhibitor (for example, methenamine) is added to the product, which slows down the chemical reaction.
The procedure is carried out as follows: the acid is diluted with water until a 5% concentration is reached and an inhibitor is added at the rate of 0.5 g per 1 liter of liquid. The resulting composition is treated with the surface and left for 30-40 minutes (depending on the degree of contamination), after which it is washed with water.
A weak acid solution is also used to remove berry stains, ink or rust from fabrics. To do this, the material is soaked in the composition for some time, after which it is thoroughly rinsed and washed as usual.
Descaling a kettle
For this purpose, use a 3-5% solution of hydrochloric acid, which is poured into a kettle and heated to 60-80 ° C for 1-2 hours or until scale deposits disintegrate. After this, the scale becomes loose and can be easily removed with a wooden spatula.
The effectiveness of the method is due to the fact that the reagent reacts with magnesium and calcium carbonates and converts them into soluble salts. The carbon dioxide released during this process destroys the scale layer and makes it loose. After removing salt deposits, wash the dishes thoroughly with clean water.
Important point! This method is not suitable for descaling enamel or aluminum kettles with chips and cracks: this will lead to corrosion of the metal and severe damage to it.
Conclusion
If precautions and safety rules are observed, hydrochloric acid will become an indispensable assistant in everyday life. And you can purchase it at the most affordable prices in our company.
Source: https://him-kazan.ru/stati/solyanaya-kislota-primenenie-v-byitu-dlya-prochistki-trub
Metal etching
Pickling is the process of cleaning and processing a metal workpiece. Chemical, acidic, alkaline, electrochemical - there are many ways to perform this technological operation. Where is metal etching used, why is it used in industry, what are the processing methods using this technology, all these issues are discussed in detail in the article below.
What is etching
This is a technology for removing the top layer from the surface of a metal part. The technology is used to clean workpieces from scale, rust, oxides and remove the top layer of metal. Using this method, the top layer is removed to search for internal defects and study the macrostructure of the material.
Using etching, they clean the part and increase surface adhesion. This is done for the subsequent connection of the metal surface with another workpiece, before applying paint, enamel, galvanic coating and other protective coatings.
The method allows you not only to quickly clean the part, but also to create the desired pattern on the metal surface. Using this method, the finest channels and complex images are cut out on a metal surface. You can clean large parts or rolled products. The processing depth is adjustable with an accuracy of several microns, which makes it possible to produce complex parts with small grooves and other complex elements.
Application of etching in industry
- For cleaning parts made of carbon, low-alloy and high-alloy steel, titanium and aluminum from oxide film.
- To improve adhesion before applying galvanic and other types of protective coatings.
- To prepare steel surfaces for hot-dip galvanizing.
- To conduct macroanalysis to detect the formation of intergranular corrosion in stainless steels.
- This technology is used to process small metal parts, such as watch gears.
- Copper processing is used to make semiconductor chips and printed circuit boards in electronics.
This method applies a conductive pattern to the microcircuit.
- For quick cleaning of hot rolled metal products, heat-treated parts, from oxides.
- In the aircraft industry, this technology is used to reduce the thickness of aluminum sheets to reduce the weight of the aircraft.
- In the manufacture of metal inscriptions and drawings.
Etching produces relief images drawn by removing a layer of metal according to a specific stencil.
Types of etching
The main types of metal processing used in industry:
- electrolytic - there are cathode and anodic;
- chemical;
- plasma.
Electrolytic etching
Electrolytic or galvanic metal processing is used to quickly clean parts, apply engravings and produce grooves. Metal parts are immersed in an acid or salt electrolyte. The part becomes a cathode - a negative electrode or an anode - a positive electrode. Therefore, two types of electrolytic etching are classified - cathodic and anodic.
- Cathodic etching. The method is used to remove scale from the surface of carbon steel products after hot rolling or oil quenching. In cathodic etching, the material for the anode is lead, and the electrolyte is a solution of hydrochloric, sulfuric acid or an alkali metal salt. During the electrolysis process, hydrogen gas is actively released at the cathode, which interacts with iron and removes scale. During the cathode method, the metal surface is actively saturated with hydrogen, which increases the fragility of the workpiece. Therefore, the cathode method is not used for thin-walled products.
- Anodic electrochemical cleaning. This is the most common method in mechanical engineering. The process involves mechanically tearing off the oxide film on the anode with oxygen and mixing metal molecules with the electrolyte. An electrolyte is a solution of acids or salts of the metal being processed. Lead, copper and other metals are used as the cathode. During anodic treatment, the surface of the product becomes clean, with slight roughness, and the metal dissolves in the electrolyte. With this method, there is a risk of reducing the thickness of the workpiece and over-etching.
Chemical etching
The chemical treatment method is used to clean the surface of a part from oxide film, scale and rust for workpieces made of the following materials:
- ferrous metals;
- stainless and heat-resistant steels;
- titanium and its alloys;
- aluminum
For etching, sulfuric, hydrochloric or nitric acid is used. The workpiece is immersed in an acid or alkaline solution, molten salt and kept for the required time interval. The required cleaning time can range from 1 to 120 minutes.
The cleaning process occurs due to the release of hydrogen when the acid interacts with the metal. Acid molecules penetrate through pores and cracks under the oxide film. There they interact with the metal surface and hydrogen is released. The released gas tears off the oxide film and cleans the part.
Simultaneously with the oxides, the metal being treated dissolves in the acid. To prevent this process, corrosion inhibitors are used.
Plasma etching
With the ion-plasma method, cleaning and removal of the surface layer occurs by bombarding the part with ions of inert gases that do not react chemically with the molecules of the material being processed. Allows you to make high-precision notches and grooves with an accuracy of up to 10 nm. The technology is used in microelectronics.
The plasma-chemical method involves excitation of plasma in a chemically active medium, which causes the formation of ions and radicals. Active particles falling on a metal surface cause a chemical reaction. In this case, light compounds are formed, which are removed from the surrounding air by vacuum pumps.
The method is based on chemical reactions that occur when using reactive gases, such as oxygen, which are highly reactive. These gases actively interact in the gas discharge plasma. Unlike plasma treatment in inert gases, with this cleaning method, the active gas reacts only with certain molecules.
The disadvantage of this method is the lateral expansion of the grooves.
Etchants
Pickling of carbon steels is carried out in an 8-20% solution of sulfuric or 10-20% hydrochloric acid. With the obligatory addition of corrosion inhibitors (KS, ChM, UNIKOL) to eliminate the fragility of the material and reduce the possibility of over-etching.
Products made of stainless or heat-resistant steel are processed using a solution consisting of: 12% hydrochloric, 12% sulfuric, 1% nitric acid. If required, processing is done in several stages. The first is that scale is loosened in 20% hydrochloric acid. The second stage is immersion in a 20-40% nitric acid solution to completely remove surface contaminants.
The thick layer of scale that forms on stainless steel is removed during its production by 75-85% molten caustic soda with 20-25% sodium nitrate. After which, complete removal of oxides is carried out in 15-20% nitric acid.
Processing of aluminum and alloys based on it involves removing the refractory oxide film from the surface of the workpiece. For this purpose, alkaline or acidic solutions are used. Usually 10-20% alkali is used, at a temperature of 50-80 ºС, the etching procedure takes less than 2 minutes. The addition of sodium chloride and sodium fluoride to the alkali makes this process more uniform.
The purification of titanium and its alloys, carried out after heat treatment, is carried out in several stages. At the first stage, scale is loosened in concentrated caustic soda. Then the scale is removed in a solution of sulfuric, nitric or hydrofluoric acid. To remove the remaining pickling sludge, use hydrochloric or nitric acid with the addition of a small amount of hydrofluoric acid.
When processing copper and its alloys, etchants from hydrogen peroxide, chromic acid and the following salts are used:
- copper chloride;
- ferric chloride;
- ammonium persulfate.
This information material describes in detail the pickling process used in metallurgical plants. The method allows you to quickly clean the metal surface from oxides, scale, rust and other contaminants. Thanks to etching, it is possible to apply various designs to metal, create complex microcircuits and make microscopic channels of the desired shape.
Source: https://prompriem.ru/stati/travlenie-metalla.html
Hydrochloric acid is one of the strongest acids, an extremely popular reagent
- Hydrochloric acid is an inorganic substance, a monobasic acid, one of the strongest acids. Other names are also used: hydrogen chloride, hydrochloric acid, hydrochloric acid. Acid in its pure form is a colorless and odorless liquid. Industrial acid usually contains impurities that give it a slightly yellowish tint. Hydrochloric acid is often called “fuming” because it emits hydrogen chloride vapors, which react with moisture in the air and form acid fog. Very soluble in water. At room temperature, the maximum possible hydrogen chloride content by weight is 38%. An acid with a concentration greater than 24% is considered concentrated. Hydrochloric acid actively reacts with metals, oxides, and hydroxides, forming salts - chlorides. HCl reacts with salts of weaker acids; with strong oxidizing agents and ammonia. To determine hydrochloric acid or chlorides, use a reaction with silver nitrate AgNO3, which results in the formation of a white cheesy precipitate.
Safety precautions
The substance is very caustic, corrodes skin, organic materials, metals and their oxides. When exposed to air, it releases hydrogen chloride vapors, which cause suffocation, burns to the skin, mucous membranes of the eyes and nose, damage the respiratory system, and destroy teeth. Hydrochloric acid belongs to substances of the 2nd degree of danger (highly dangerous), the maximum permissible concentration of the reagent in the air is 0.005 mg/l. You can work with hydrogen chloride only in filter gas masks and protective clothing, including rubber gloves, an apron, and safety shoes. When acid spills, it is washed off with plenty of water or neutralized with alkaline solutions. Those affected by the acid should be taken out of the danger zone, rinse their skin and eyes with water or soda solution, and call a doctor. The chemical reagent can be transported and stored in glass, plastic containers, as well as in metal containers coated on the inside with a rubber layer. The container must be hermetically sealed.
Receipt
On an industrial scale, hydrochloric acid is produced from hydrogen chloride (HCl) gas. Hydrogen chloride itself is produced in two main ways: - by the exothermic reaction of chlorine and hydrogen - thus obtaining a high-purity reagent, for example, for the food industry and pharmaceuticals; - from accompanying industrial gases - an acid based on such HCl is called free gas.
This is interesting
It was hydrochloric acid that nature “entrusted” with the process of breaking down food in the body. The concentration of acid in the stomach is only 0.4%, but this is enough to digest a razor blade in a week!
Acid is produced by the cells of the stomach itself, which is protected from this aggressive substance by the mucous membrane. However, its surface is renewed daily to restore damaged areas. In addition to participating in the process of digesting food, acid also performs a protective function, killing pathogens that enter the body through the stomach.
Application
- In medicine and pharmaceuticals - to restore the acidity of gastric juice in case of insufficiency; for anemia to improve the absorption of iron-containing drugs.— In the food industry, it is a food additive, acidity regulator E507, and also an ingredient in seltzer (soda) water. Used in the production of fructose, gelatin, citric acid.
- In the chemical industry - the basis for the production of chlorine, soda, monosodium glutamate, metal chlorides, for example, zinc chloride, manganese chloride, ferric chloride; synthesis of organochlorine substances; catalyst in organic syntheses.
— Most of the hydrochloric acid produced in the world is consumed in metallurgy for cleaning workpieces from oxides. For these purposes, an inhibited industrial acid is used, which contains special reaction inhibitors (moderators), due to which the reagent dissolves oxides, but not the metal itself. Metals are also etched with hydrochloric acid; they are cleaned before tinning, soldering, galvanizing.—They treat the leather before tanning.—In the mining industry it is in demand for cleaning boreholes from sediments, for processing ores and rock formations.—In laboratory practice, hydrochloric acid is used as a popular reagent for analytical studies and for cleaning vessels from difficult to remove contaminants.
— Used in the rubber, pulp and paper industries, and in ferrous metallurgy; for cleaning boilers, pipes, equipment from complex deposits, scale, rust; for cleaning ceramic and metal products.
Source: https://pcgroup.ru/blog/solyanaya-kislota-odna-iz-samyh-silnyh-kislot-chrezvychajno-vostrebovannyj-reaktiv/
Surface etching. Part 1
During manufacturing and storage, metal products are exposed to the environment, as a result their surface becomes covered with corrosion products or thermal scale . This layer not only worsens the appearance of the products, but also complicates subsequent technological operations.
Before deposition of galvanic coatings on products, their surface must be cleaned of all contaminants and oxides. Contaminants are removed during the degreasing process (see “Degreasing the surface.”). The surface is cleared of oxides and thermal scale during the etching process .
Etching can be carried out in solutions chemically or electrochemically
Electroplating line for surface etching
Chemical etching is carried out by immersing products in an etching solution without exposure to electric current.
The largest percentage of parts coated in the galvanic shop are made of low-carbon steel, which have an oxide layer on the surface that is uneven in thickness. The scale layer is porous, therefore, when etching in acid solutions, partial dissolution of the metal occurs along with oxides.
For etching ferrous oxide, solutions of sulfuric and hydrochloric acids are mainly used. It is necessary to carry out the etching process in such a way that etching in the base metal solution is minimal. This depends on the composition of the solution, the concentration of acids and temperature.
In a solution of hydrochloric acid, unlike sulfuric acid, etching of scale occurs due to its chemical dissolution. In practice, 10–20% solutions of hydrochloric acid are used at room temperature. When etching in a sulfuric acid solution, the optimal concentration is 20 - 25%, temperature 50 - 600C. Considering the different nature of the effect of acids on iron and its oxides, mixtures of solutions are used for etching: sulfuric acid - 5%, hydrochloric acid - 15% or sulfuric acid 10%, hydrochloric acid - 10%.
The etching process , in addition to removing scale, is accompanied by the release of hydrogen, and hydrogenation of the surface , leading to embrittlement. To prevent the sorption of hydrogen by the metal, inhibitors are introduced into the etching solutions: catapine K-I-1, syntanol, urotropine, etc. in an amount of 3 - 5 g/l.
When etching alloy steels in solutions , due to the presence of thermal scale, the use of more active solutions is required. It is advisable to carry out etching in solutions in two stages: loosen the main layer of scale in a solution of 20% hydrochloric or sulfuric acid, and finish the etching in a solution of 20–40% nitric acid.
To speed up the surface cleaning process, an electrochemical etching method is used, which can be carried out both on the anode and on the cathode
In anodic etching, the oxide film is first etched in a solution, and then a passive film is formed. The etching process is intense, so it is important not to overetch the surface of the part, which is the anode. Anodic etching is used for simple-shaped parts made of carbon and alloy steel.
Compositions of electrolyte solutions for anodic etching of carbon steels, g/l:
Solution 1:
Sulfuric acid 200 – 250 Iron sulfate 7-aqueous 1 – 2 Sodium chloride 20 – 25
Solution temperature 40 – 500C, DA= 5 – 10 A/dm2, time 10 – 20 minutes
Solution 2:
Hydrochloric acid 8 – 10 Sodium chloride 40 – 50 Iron chloride 6-aqueous 140 – 150
Solution temperature 18 – 350C, DA= 5 – 10 A/dm2, time 5 – 10 minutes
The anodic current density is selected depending on the state of the surface during etching in an electrolyte solution and the required speed of the process.
Compositions of electrolyte solutions for cathodic etching of carbon steels, g/l:
Solution 1:
Sulfuric acid 100 – 150
Solution temperature 40 – 500C, DC = 3 – 10 A/dm2, time 10 – 15 minutes.
Solution 2:
Sulfuric acid 50 – 60 Hydrochloric acid 25 – 30 Sodium chloride 15 – 20
Solution temperature 60 – 700C, DA= 10 – 15 A/dm2, time 10 – 15 minutes
Cathodic etching in an electrolyte solution is used primarily to remove oxides from the surface of parts subjected to heat treatment and oil quenching. Lead is used as an anode.
If you have difficulty cleaning the surface, contact us for services.
Attention! Electroplating training course! Find out more
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Source: http://blog.tep-nn.ru/?p=1644
Zinc corrosion
Zinc corrosion is the destruction of metal under the influence of an aggressive corrosive environment.
For the process Zn2+ + 2e → Zn, the standard electrode potential of zinc is -0.76 V.
The melting point of zinc is 419.6 °C.
Zinc density is 7.133 g/cm2.
Corrosion of zinc can occur with both hydrogen and oxygen depolarization.
The maximum stability of zinc and zinc coatings is observed in the pH range 9 – 11. At lower or higher values, corrosion of zinc increases significantly.
Corrosion of zinc in water
Corrosion of zinc in water occurs at temperatures above 55 °C. As the temperature increases, the corrosion rate increases, with a maximum observed at a temperature of 70 °C. After this, the destruction of the metal occurs very slowly. This is due to the formation of corrosion products in water on the surface of zinc.
At temperatures up to 55 °C and above 90 – 95 °C, corrosion products have fairly high protective properties, forming a dense continuous film on the surface. The maximum corrosion rate of zinc is explained by the formation of a loose film consisting of Zn(OH)2, which does not have good protective properties, because
peels off easily.
In neutral solutions, zinc corrosion occurs with oxygen depolarization.
In sea water, zinc coating of steel can be called quite effective. About 0.03 mm of zinc is consumed per year. The service life of a 0.13 mm thick zinc coating is about 4 – 5 years, which is quite a long time for such an aggressive environment. For aluminum and its alloys in seawater, zinc acts as a protector.
To reduce the rate of corrosion of zinc in an aqueous environment, the following inhibitors are used: sodium silicate and sodium dichromate, sodium hexametaphosphate, lanolin, borax.
Atmospheric corrosion of zinc
Corrosion of zinc does not occur in atmospheric conditions. This is due to the formation of a thin protective film of basic zinc oxide – ZnO – on the surface. Zinc is characterized by fairly high corrosion resistance even in the marine atmosphere. The surface is coated with zinc hydroxide and its basic carbon dioxide salts. When exposed to a marine atmosphere, a zinc coating with a thickness of 0.03 mm protects the surface of the product well for eight years.
The industrial atmosphere (with impurities of SO2, SO3, HCl) negatively affects the corrosion resistance of zinc. The service life of a zinc coating of the same thickness is limited to four years. The rural atmosphere does not have any particular negative impact, the service life is about 11 years.
Corrosion of zinc in acids
Both zinc of ordinary purity and its oxide corrode when in contact with acids. Very pure zinc does not react with solutions of acids and alkalis even when the temperature rises. The reaction begins only when copper sulfate (CuSO4) is added. Corrosion of zinc is also observed in solutions of alkaline and acidic salts.
In acids and acidified environments, zinc corrosion occurs with hydrogen depolarization, i.e. release of hydrogen.
Corrosion of zinc in hydrochloric acid proceeds intensively, with the formation of zinc chloride and the release of hydrogen according to the reaction:
Zn + 2HCl → ZnCl2 + H2.
One of the uses of hydrochloric acid is precisely the production of zinc chloride.
Corrosion of zinc in sulfuric acid also occurs quite intensively, with the formation of zinc sulfate and the release of hydrogen according to the reaction:
Zn + H2SO4(dil.) → ZnSO4 + H2.
Corrosion of zinc in alkalis
Zinc reacts actively with alkalis, forming hydroxinates.
Zn + 2NaOH + 2H2O → Na2[Zn(OH)4] + H.
Zinc corrosion occurs intensively when in contact with an ammonia solution:
Zn + 4NH3•H2O → [Zn(NH3)4](OH)2 + 2H2O + H2
In this case, an ammonia complex [Zn(NH3)4](OH)2 is formed.
When zinc comes into contact with a metal that has a more electropositive potential, the rate of zinc corrosion increases significantly. Zinc is used as a protector for more noble metals.
Although zinc is a fairly corrosion-resistant metal, it has not found application in the food industry, because upon contact with acidic foods, it forms toxic salts.
Source: https://www.okorrozii.com/korrozia-zinka.html
Soldering acid recipes
When carrying out soldering, acidic fluxes are often used to pretreat the surface of parts. The degree of activity of the material is selected depending on the type of metal and the degree of its contamination.
There are various products on sale, the composition of which is selected taking into account the specifics of the work to be done. You can make soldering acid at home yourself.
This will require certain knowledge, basic ability to make chemical compositions and a small amount of money to purchase components.
Why is acid flux needed?
Metals include highly active substances. Many of them oxidize easily and quickly in the presence of air. The resulting oxides are converted into hydroxides under the influence of atmospheric moisture.
A mixture of oxidation products is clearly visible on iron products after storage in air. It's called rust. Other metals are also coated with an oxide layer, which prevents anything from being soldered to the product.
Acid fluxes help to cope with the problem, the simplest of which is soldering acid. Under this name, several different single-component or complex compositions are collected, many of which can be prepared with your own hands.
What can you do at home?
The degree of acidity of fluxes differs. Active mixtures include compositions with zinc chloride. From the school course, perhaps someone remembered the properties of saline solutions.
Salts tend to undergo hydrolysis in the presence of water. Zinc chloride, when exchanged with water, forms a strong acid and a weak alkali. Therefore, the solution has an active acidic character. Hydrochloric acid quickly removes oxide substances.
Typically, soldering acid is made by adding 412 g of zinc to 1 liter of concentrated hydrochloric (hydrochloride) acid. The procedure is not entirely pleasant and safe. During operation, volatile acidic vapors are released.
You should work with concentrated hodgepodge only under a hood or in a respirator, in a well-ventilated room.
With hydrochloric acid
Several formulations with zinc chloride are popular. Zinc compounds are used in the galvanizing process to protect metals from corrosion. This chemical element is known for its resistance to oxidation processes. Making soldering acids with your own hands is not difficult.
For products made of ferrous and non-ferrous metals, the following ratio is suitable:
- zinc chloride – minimum 25%, maximum – 30%;
- concentrated hydrochloric acid – 0.7%.
Both components must be quickly dissolved in water. It should be noted that hydrochloric acid is a highly volatile substance. It is advisable to work with it under a hood. The bottle with the starting reagent should only be kept closed.
With Vaseline and alcohol
For parts made of ferrous and non-ferrous metals, sometimes it is more convenient to use a paste with acidic properties instead of soldering acid.
To prepare it, you need to mix a saturated solution of zinc chloride - 3.7% and technical petroleum jelly - 85%. To give the required consistency, add a little water to the mixture.
To work with nickel, platinum and their alloys, you can make a soldering mixture with your own hands from zinc chloride - 1.4% and ethyl (wine) alcohol - 40%. Both components must be thoroughly dissolved in water and the finished soldering solution must be mixed.
After using all the above compounds, the soldering area should be rinsed well with plain water.
With rosin
For carrying out critical work with ferrous metals, soldering precious and non-ferrous metals, a paste mixture made by yourself from rosin - 24% and zinc chloride - 1% is suitable. All this must be dissolved in ethyl alcohol. At the end of the soldering procedure, you need to wash the work area with acetone.
To form a seam with increased strength characteristics, it is recommended to take:
- rosin – 16%,
- zinc chloride – 4%,
- technical petroleum jelly – 80%.
It is more difficult to rinse the soldering area after treating it with such homemade solder paste. You need to take acetone.
Experience shows that in some cases it makes sense to replace soldering acid with a corresponding acidic paste.
Homemade sour pastes
When working with aluminum parts, a flux with oleic acid is often used, the formula C17H33COOH gives an idea of the high molecular weight. Higher acid has a viscous consistency, similar to a slightly viscous liquid.
Soldering flux is made as follows: 20 ml of oleic acid, about 3 g of lithium iodide are dissolved in a glass container in a water bath. A homogeneous solution, made with your own hands, after cooling, is poured into a glass bottle for storage.
After soldering, the working area is washed with acetone, gasoline or alcohol.
To solder nichrome, you can make a composition with your own hands from 100 g of Vaseline, 7 g of powdered zinc chloride, 7 g of glycerin.
The whole mass must be mixed well. It is advisable to do this in a thick porcelain cup or a special mortar.
Other available options
Phosphoric acid is widely used for processing iron, steel, and nickel alloys. It is often called simply phosphorus. This acid can be used to treat the surface of pure copper.
On all metals, phosphoric acid not only removes oxides, but also forms a protective layer.
During soldering work, the top layer of phosphates is easily destroyed by a heated soldering iron tip. The solder mass is evenly distributed on the processed parts. The result is a strong connection.
Perhaps the simplest option for replacing soldering acid is regular aspirin. The solution is quickly prepared with your own hands. You need to take a regular cheap tablet and dissolve it in a small amount of water. Sometimes craftsmen simply sprinkle crushed aspirin on the soldering area.
There is ready-made VTS flux on sale, which, in fact, is also soldering acid. You can make a similar product yourself.
You need to take salicylic acid, Vaseline, triethanolamine. Dissolve all components in alcohol. Flux is successfully used to work with copper, platinum, silver and their alloys.
Source: https://svaring.com/soldering/flus/recepty-pajalnoj-kisloty
DIY soldering acid
Soldering acid is a flux that can be classified as a separate category, because it has an aggressive effect on materials that are needed during work. This flux mainly spreads in a liquid state, and this does not depend on its concentration. Sometimes you can purchase a concentrated substance and then dilute it, or perhaps buy a ready-made, diluted one. In addition, everyone can easily make soldering acid on their own.
The properties of materials must be selected according to those factors that are necessary for their use.
Soldering acid is intended for those metals that are heavily contaminated, because oxidation occurs on them, and a large amount of rust remains on the surface.
The material is very active, so it is necessary to work with it carefully and avoid contact with human skin and mucous membranes. You must first carefully familiarize yourself with the rules and methods of using acid, and only then begin to use it for its intended purpose.
In the process of producing soldering acid yourself, it is necessary to use special technology. In the end, the result should be a material that will have the properties prescribed by GOST. This is what will make the flux high-quality and reliable so that the connections are strong.
It is necessary to ensure that the properties and functions of the acid work even after soldering the metals, because the material removes films and rust from the surface, and also prevents their reappearance.
You should also take into account the spreadability of the materials being soldered over the surface and the adhesion to metals and products.
