What is titanium anodizing

Anodized aluminum

Modern devices made of metal are very different from those made 30-50 years ago. They have become lightweight, resistant to harmful influences, and minimally dangerous to life. Anodized aluminum occupies one of the leading places among the metals that are used for the manufacture of such devices.

Anodized aluminum has long and firmly taken the place of steel and cast iron where, in addition to strength and resistance to external influences, other main qualities are required - lightness and ductility. It is much lighter than steel, so it has successfully replaced it in tens of thousands of products used in a variety of fields - industry, medicine, tourism, sports.

With the advent of anodizing technology, the remarkable properties of aluminum were supplemented by the results of chemical modification - high corrosion resistance and resistance to mechanical stress.

What is anodizing

The anodizing process is an electrolytic chemical reaction of a metal with an oxidizing agent. A thin layer of oxide is applied to a metal surface, which acts as an anode during the reaction.

Due to polarization in an electrolytic conducting medium, both pure metals and various alloys can be coated with a thin oxide film. The oxide layer effectively protects against corrosion and fading when exposed to direct sunlight.

The most in demand in industry are anodized alloys of aluminum and magnesium.

The ultimate goal of anodizing is to create a so-called AOP - anodic oxide film - on the surface of an aluminum sheet. It performs two main functions:

1. Protection from external influences;
2. Decoration.

In the second case, dyes of various colors with a strictly defined chemical composition are added to the conducting medium.

Engineers from the UK were the first to introduce industrial anodization of aluminum into production. The light and durable metal created in this way began to be used in the aviation industry. Later, a standard for metal anodization appeared, which is successfully used in modern aircraft construction. It has the nomenclature marking DEF STAN 03-24/3.

The coating consists of two components:

• organic;
• anode-chromium.

Paint applied in accordance with the standard is very resistant to abrasion and other mechanical damage.

Anodizing technology

Today, the most widespread process is aluminum sulfate anodization. Its essence is as follows:

1. The part and the cathode, made of lead, are placed in a bath with an electrolyte - sulfuric acid H2 SO4 - to remove impurities and oils. Indicators of physical quantities: solution density – 1,200-1,300 g/l; current density during anodizing process – 10-50 mA/cm²; source voltage – 50-100 V; electrolyte temperature – 20-30 °C (for subsequent painting – no more than 20 °C).
2. A final rinse is carried out in a caustic solution.
3. A thin oxide layer is created on the surface of an aluminum part.

The growth rate of the anodic layer on the metal surface is uneven and very low. The optimal amount of colored oxide is applied when the current density reaches 1.5-1.6 A/dm². At lower values, the layer turns out to be almost colorless.

Large values ​​of cathode density (the ratio of the size of the cathode to the size of the surface being processed) cause difficulties when processing massive parts - the appearance of burnouts and etching.

The optimal cathode area is x2 in relation to the size of the workpiece.

It is also very important to control the clamp and electrical contact of the part with the suspension.

In addition to sulfuric acid, other substances and compounds can be used as an electrolyte during anodizing:

• oxalic acid;
• organic compounds and mixtures;
• orthophosphoric acid.
• chromic anhydride.

The process technology does not change. The ultimate goal when choosing an electrolytic medium is to obtain a layer with certain physical characteristics before repainting.

Warm anodizing

The warm anodizing process is carried out at an ambient temperature of 15-20 °C. Parts processed in this way have two negative features:

1. Not very high anti-corrosion resistance. When in contact with a chemically aggressive environment or metal, the anodized layer is exposed to oxygen.
2. Low degree of protection against mechanical influences. It is quite possible to cause mechanical damage to the anodized layer with a sharp tip.

The warm anodizing process consists of six stages:

• cleaning the surface of the part from grease.
• fastening on a suspension.
• anodizing until a light milky color appears.
• rinsing with cold water.
• dyeing with a hot solution of aniline dye.
• allowing the anodized metal to sit for 30 minutes after painting.

The layers of film produced by warm anodizing are exceptionally beautiful. This type of aluminum is best used in structures that are not exposed to harsh external influences. In addition, the anodized layer is an excellent base for repainting due to its superior dye adhesion. The applied paint will last for a very long time.

Cold anodizing

The technology of cold application of the anodic layer involves processing aluminum at temperatures from -10 to +10 °C. The quality of metal processed in this way is incomparably higher than with warm anodizing.

Aluminum receives excellent physical characteristics:

• high strength.
• low rate of layer dissolution.
• greater film thickness.

When cold anodizing it is necessary to carry out the following procedures:

• degreasing the surface to be treated.
• placing the part on the hanger.
• anodizing until a dense shade is obtained.
• washing in water at any temperature.
• fixing the anode layer in steam or hot distilled water.

A distinctive feature of the process is the long forced cooling time. After this, the anodized aluminum layer becomes completely impervious to aggressive environments. Only titanium, after several decades, is able to slightly reduce the physical characteristics of cold-process anodized aluminum.

The coating is characterized by exceptional beauty and wear resistance. The technology has only one drawback: when repainting, you can only use inorganic compounds.

Why is aluminum anodized and how is it used?

The purpose of anodizing parts made of aluminum is to increase service life under exposure to various aggressive environments.

Given that pure aluminum has a high affinity for oxygen, its corrosion resistance is higher than that of many other light metals for structural purposes. Natural oxidation of aluminum occurs upon first contact with air. The process of anodic treatment further increases the tendency of both chemical elements to create oxides by reacting with each other.

The ability of the anodic film to perfectly absorb dyes of various chemical compositions makes aluminum processed in this way an excellent decorative material. It is widely used for external finishing of interiors of buildings and structures.

Aluminum structures are indispensable when creating:

• advertising structures for cultural and sports events, exhibitions and shows.
• information stands for mass actions, rallies, meetings.

The excellent reflective ability of anodized aluminum has made it an indispensable material in the manufacture of road signs. Thanks to interference, the information printed on the sign during anodization is clearly visible to motorists at night.

Amateur bicycle frames are also made from anodized aluminum alloys. The special clothing worn by cyclists at night is coated with a thin film of aluminum oxide. Thanks to this, the silhouette is easy to see in the dark at a respectful distance. For the same purpose, anodized metal is used in the manufacture of a reflective layer in floodlight installations.

The excellent properties of anodized aluminum allow it to be used for the manufacture of a wide range of parts and assemblies used in a wide variety of fields. We can safely say: if the decision is made to make something from metal processed in this way, the strength and lightness of the structure will not raise any doubts!

Source: https://prompriem.ru/splavyi/anodirovannyj-alyuminij.html

Anodizing steel, aluminum

Anodizing a metal refers to the procedure of growing an oxide film using anodic oxidation. This procedure can be carried out for almost any metal.

But most often we are talking about steel, aluminum and non-ferrous metals (mainly titanium and tantalum). In turn, anodizing copper and iron turns out to be very difficult. This is due to the fact that the indicated metals form not one stable oxide, but two.

This negatively affects adhesion and significantly increases the risk of cracking of the oxide film.

Anodizing operation and its specifics

Here you can see 2 baths with washing liquid (blue) and anodizing liquid (green liquid)

Anodizing metal as a procedure is not particularly difficult and, if desired, can be done on your own. Performing this operation involves performing the following work steps:

Stage 1. Preparing the metal surface

Before starting anodic oxidation, the metal surface should be carefully prepared: polished, ground. The surface is degreased using organic solvents (for example, gasoline, acetone or alcohol). Then the surface is treated with any alkali.

At home, an ordinary soap solution can be used. Ferrous metals are perfectly degreased using a solution of caustic potassium or soda, which is preheated to 80 degrees. As for aluminum, a 10% sodium phosphate solution is better suited for it.

Stage 2. Etching (picking) the metal surface

Etching a metal surface is carried out in order to remove oxides that interfere with the high-quality application of a new coating. To carry out the procedure, sulfuric acid is used (in a ratio of 80 milliliters of acid per 100 milliliters of input with the addition of 2 grams of chromium.

Stage 3. Anodizing the metal

The process of anodic oxidation of a metal is carried out in an electrolyte solution under the influence of direct current. It is important that the container in which anodizing is performed does not allow current to pass through. A 20% sulfuric acid solution is most often used as an electrolyte.

IMPORTANT! When preparing an electrolyte solution, it is necessary to pour sulfuric acid into water, and not vice versa.

In the absence of sulfuric acid, a solution of table salt and soda can be used.

The anodic oxidation process itself occurs as follows. A metal product is attached to the anode using a special suspension, and a lead plate is attached to the cathode (for products with complex shapes, several lead plates will be required).

The distance to the plate should be no more than nine centimeters . The procedure is carried out at a temperature of 20 degrees. In this case, the electric current density should vary from 2 to 3 A/sq. dm .

Voltage required is from 12 to 15 V. The whole process takes about one hour.

Devices and tools

Before you begin anodic oxidation, you should prepare the following equipment and tools that will be needed to complete the job:

• aluminum foil;
• rubber gloves;
• plastic container for placing a metal product;
• 9V batteries (from 1 to 8 pcs.);
• insulated cable (about one and a half meters);
• electrolyte solution;
• spoon;
• organic solvent;
• plastic glass;
• mites;
• a device designed for stripping cables.

Installations for anodizing metals and their design features

Any large installation for anodic oxidation is a rather complex complex, including electrical, chemical and mechanical equipment. When choosing it, you should take into account a number of significant points:

1. The highest operating costs are for unloading as well as loading procedures . And this is precisely what makes anodic oxidation a very labor-intensive procedure.
2. The maximum throughput of the anodizing installation is determined by the power of the DC rectifier , with the help of which anodic oxidation is carried out. The most commonly used rectifier is 25 Watt . It is good if the installation has stepless voltage regulation under load from zero to maximum , as well as an automatic function of returning the voltage to zero at the end of the cycle. High-quality anodic oxidation requires the presence of an oxide film on the metal surface. At the very beginning of the anodizing process, the film is relatively thin and has low resistance. Accordingly, in order to maintain the current density, a small voltage is sufficient . As the thickness of the oxide film increases, its resistance increases, and accordingly the current decreases. In order to maintain the same current density throughout the procedure, the voltage must be gradually and smoothly increased. And this is where the infinitely variable voltage control of the anodizing machine comes in very handy.
3. The contacts between the plates and the busbars require precision design. Therefore, it is advisable to install flexible contact pads (for example, made of copper) at the ends of the anodizing baths.

Features of anodizing copper and its alloys

Most often, anodization of copper and its alloys is carried out by chemical or electrochemical methods. As a result, the surface of the material in most cases acquires a colored coating.

To obtain a film of copper, an acidic or cyanide liquid is used. Copper alloys, which contain alloying metals, undergo anodic oxidation much more difficult.

Features of silver anodizing

Anodic oxidation of silver allows you to give an initially white metal a black, purple or blue tint without changing the structure and quality characteristics of the material being processed.

Experts recommend processing silver items using sulfur liver. When anodizing, silver begins to change color after about half an hour.

After the product has acquired the required color, it must be removed from the liquid and rinsed thoroughly, first with hot, then warm and finally cold water.

Features of titanium anodizing

Anodizing titanium is a mandatory procedure, the main significance of which is to increase the wear resistance of this metal. The presence of an oxide film gives the product chemical strength and changes the color of the coating surface. Chromic, oxalic or any other acid can be used for the anodic oxidation of titanium.

Dependence of the color of the titanium oxide film on the current voltage during oxidation.

Features of aluminum anodizing

Anodic oxidation of aluminum is required, regardless of the fact that this metal can still look great after extrusion. This is due to the fact that aluminum is highly susceptible to corrosion. In addition, it is easily destroyed under the influence of a number of negative external factors.

Why is metal anodizing necessary?

The scope of application of anodic oxidation is quite diverse. Metals that have undergone anodic oxidation acquire:

• excellent protective properties;
• homogeneous surface;
• no stripes or scratches;
• high decorative characteristics

Recently, decorative anodizing of metal has been in quite high demand, which can be done both with or without mechanical processing.

Most often, anodic oxidation of a metal is carried out to protect the alloy from the development of corrosion.

Below is a short video of the aluminum anodizing operation.

Source: http://www.m-deer.ru/tehnologiya/anodirovanie.html

Anodizing titanium at home - Metals, equipment, instructions

Translated by alexlevchenko92 for mozgochiny.ru

Anodizing titanium is an extremely interesting and useful activity that is very easy to do your own hands at home.

Anodizing is used in industry to improve the (corrosion) resistance of metals.

In addition, it is also used as a decorative decoration for jewelry (due to the wide range of colors obtained).

Step 1: Electrolysis

The first method of anodizing titanium is based on the principles of electrolysis. A piece of titanium will act as a positive anode, which should be immersed in a bath of electrolyte. (borax or sulfuric acid is usually used).

Step 2: Materials and Tools

• Aluminium foil;
• A plastic container large enough (to hold the piece of metal being anodized);
• From 1 to 8 9V batteries;
• 1.5 m of insulated wire;
• Sodium tetraborate (Borax);
• Hot water;
• Spoon;
• Latex gloves;
• Acetone or alcohol;
• A plastic cup.

Tools (optional):

• Ticks;
• Wire stripper.

Step 3: Prepare the electrolyte

Take borax and hot water, mix everything in a cup. Stir the solution until all the borax is dissolved.

Take aluminum foil and completely cover the plastic container with it. Wrap excess foil at the top edge of the container.

Step 4: Power Supply

Remove about a centimeter of insulation from both ends of the wire (60 cm long). After this, we will make a small hole in one of the corners of the aluminum foil. Pull one end of the wire into the hole and twist everything together.

Pour the prepared electrolyte into the container.

Let's take the required number of 9 V batteries and connect them as shown in the figure. Then we connect the wire that is attached to the foil to the negative terminal of the battery. Let's take another wire and connect it to the positive of the battery (this wire will be attached to a piece of titanium).

Step 5:

Different voltages will create different colors on the titanium surface. Please note that you can always change the color by increasing the voltage, but you will not be able to return to colors produced at a lower voltage.

The image shows the sulfuric acid anodizing process, but the results are very similar to borax anodizing. If you are not sure about the voltage value, you need to perform a series of experiments with a gradual increase in voltage value.

Step 6: Cleaning the Titanium

We will wear rubber gloves to prevent fingerprints from appearing on the surface of the titanium after cleaning. Then wipe the surface with alcohol.

Step 7:

Let's take a piece of titanium and attach a positive electrode to it. Let's immerse it in the solution. In this case, you should make sure that the wire does not touch the liquid and the titanium does not touch the foil. This may result in a short circuit (in case of contact).

Once the desired color is achieved, extract the titanium and dry it. You will see the color change due to your fingerprints.

This is completely normal (the original color can be restored with acetone or alcohol).

Step 8: Thermal Method

This method uses high heat, which will “thicken” the oxide layer on the surface of the titanium. I highly recommend using a blowtorch (although you can use a gas stove).

Step 9: Materials/Tools

Source: https://spb-metalloobrabotka.com/anodirovanie-titana-v-domashnih-usloviyah/

Metal anodizing

• Characteristics
• Process
• Materials

• Aluminum
• Titanium
• Steel
• Copper
• Anodizing at home

In the modern world there are a large number of methods for processing metals and metal products. They are used both on an industrial scale and at home.

Anodizing Characteristics

Anodizing is a procedure for forming an oxide film on the surface of various metals by anodic oxidation. The growth of the oxide film is carried out in a conducting medium. This film adheres quite well to the metal surface.

The growth of the oxide film can also be carried out using the method of increasing the temperature regime. However, it turns out to be low in strength and does not last for a long time. Thanks to the electrochemical method of forming the oxide film, it is of optimal thickness and adheres well to the surface of the material.

Different types of metals can be anodized. The main requirement is that they must be able to form only one oxide. It must have the maximum level of stability. If a metal has the ability to form several oxides at once, this can lead to the film simply starting to crack and no protective effect appearing. It is for this reason that cases of anodizing iron or copper occur only at rare industrial facilities.

In addition, the oxide film on the surface of metals must have a porous structure. This is necessary so that electrolytes penetrate into it better. As a result, it turns out that only a small part of all metals on earth can satisfy these parameters. These include aluminum, tantalum, titanium. In the industrial and domestic spheres, the most common treatment is anodizing aluminum material.

Anodizing process

The technology for anodizing various types of metals is simple. The main thing is to have at hand everything you need to implement it.

It is carried out in several stages:

• Preparation of metals for the formation of an oxide film.

At this stage, preparatory work for anodizing is carried out. They consist of thoroughly cleaning and washing the metal surface. First, all dirt and deposits are removed. Then the material is washed using water or special solutions. After this procedure it must be dried.

At this stage, a solution with an acidic or any other medium is prepared and connected to the positive plus of the current source.

• Coating the surface of metals or their alloys with an oxide film.

At this stage, the metal or product made from it is immersed in the prepared solution.

Anodizing materials

Today, various metal materials are used for anodizing.

Currently, the following types of anodizing are distinguished depending on the materials used, such as:

Aluminum anodizing

This process is most common today. It consists of coating an aluminum material with an oxide film. In the process, aluminum is lowered into an acidic environment, and the positive plus of the current source is passed to it. As a result, a thin oxide film appears on the material.

Titanium anodizing

Everyone knows that titanium belongs to the category of metals that are widely used in industry, but they have a low level of wear resistance. To give it strength and resistance to different environmental conditions, an anodizing procedure is used. In this case, all anodic processing of the metal is carried out in an acidic environment at a temperature of 40 to 50 degrees Celsius.

Anodizing steel

Anodizing steel is a complex process. For this, either an alkaline or acidic medium is used. As a result, an oxide film is formed, which imparts a high level of strength.

Copper anodizing

Copper is a fairly flexible type of metal. Various methods are used to give it strength. One of them is anodizing. By placing the copper material in an acidic environment, a dense oxide film is formed on the surface, which gives the material a large number of useful characteristics.

Table. Compatibility table of metals and alloys

MaterialAluminiumBronzeDuraluminBrassCopperNickelTinTin-lead alloy (POS solder)Unalloyed steel (carbon) / cast ironChromeZinc

Aluminum	Joint	Not compatible	Joint	Not compatible	Not compatible	Not compatible	Not compatible	Not compatible	Joint	Not compatible	Joint
Bronze	Not compatible	Joint	Not compatible	Joint	Joint	Joint	Soldering	Soldering	Not compatible	Joint	Not compatible
Duralumin	Joint	Not compatible	Joint	Not compatible	Not compatible	Not compatible	Not compatible	Not compatible	Joint	Not compatible	Joint
Brass	Not compatible	Joint	Not compatible	Joint	Joint	Joint	Soldering	Soldering	Not compatible	Joint	Not compatible
Copper	Not compatible	Joint	Not compatible	Joint	Joint	Joint	Soldering	Soldering	Not compatible	Joint	Not compatible
Nickel	Not compatible	Joint	Not compatible	Joint	Joint	Joint	Soldering	Soldering	Joint	no data	Joint
Tin	Not compatible	Soldering	Not compatible	Soldering	Soldering	II	Joint	Joint	Joint	no data	Joint
Tin-lead alloy(POS solder)	Not compatible	Soldering	Not compatible	Soldering	Soldering	Soldering	Joint	Joint	Joint	no data	Joint
Unalloyed steel (carbon)/cast iron	Joint	Not compatible	Joint	Not compatible	Not compatible	Joint	Joint	Joint	Joint	Joint	Joint
Chromium	Not compatible	Joint	Not compatible	Joint	Joint	no data	no data	no data	Joint	Joint	Joint
Zinc	Joint	Not compatible	Joint	Not compatible	Not compatible	Joint	Joint	Joint	Joint	Joint	Joint

Anodizing at home

In the modern world, a large number of metal objects are used in the household sphere, which are used for various purposes. Each owner wants to protect them from corrosion so that they last a long period of time. Anodizing at home is suitable for this purpose.

Important: The procedure for home anodizing of any metal must be carried out outdoors or on the balcony.

First you need to prepare a solution. To do this, you need to mix distilled water and acid in a certain proportion. It is important to handle sulfuric acid with extreme care, because if it comes into contact with the eyes or skin, it can lead to an unpleasant situation.

After this, you can prepare metal parts for processing. All kinds of substances are used for this purpose. They are able to clean them for the procedure.

At the last stage of home anodizing, metal parts are immersed in a solution and an electric current is connected.

anodizing at home

Source: http://lkmprom.ru/clauses/tekhnologiya/anodirovanie-tekhnologiya-dannogo-protsessa/

Anodizing titanium at home with your own hands

Translated by alexlevchenko92 for mozgochiny.ru

Anodizing titanium is an extremely interesting and useful activity that is very easy to do your own hands at home. Anodizing is used in industry to improve the (corrosion) resistance of metals. In addition, it is also used as a decorative decoration for jewelry (due to the wide range of colors obtained).

Anodizing titanium at home - Machine tools, welding, metalworking

Anodizing is a process in which a coating of oxides is formed directly on the surface of metals by heating, exposure to chemicals (see "Oxidation of titanium. Part 1.") or using electricity.

The most common method of forming an oxide layer on the surface of titanium is the process of titanium oxidation under the influence of electric current, in which the titanium part is placed in a conductive solution and connected to an anode. Lead or stainless steel plates are used as the cathode.

Anodic oxidation of titanium is carried out for the purpose of:

• additional protection against corrosion;
• increasing adsorption capacity;
• increasing wear resistance;
• reducing scuffing;
• improving the decorative quality of the surface.

In production, titanium oxidation is carried out by anodic treatment of parts in solutions of sulfuric, oxalic, phosphoric, chromic acids or mixtures thereof, sometimes with the addition of other components.

Compositions of solutions to increase corrosion resistance:

Solution No. 1:

Sulfuric acid 50 – 60 g/l

Temperature 15 – 25°C, current density 1.0 – 1.5 A/dm2.

Processing time 50 – 60 min.

When anodizing titanium, the first 2–6 minutes maintain a given current density, the voltage across the bath increases to 90–110 V, after which the current density drops to 0.2 A/dm2. The further process of anodic oxidation of titanium is carried out without adjusting the current. The process is carried out while stirring the electrolyte. Cathodes are made of lead or steel X18N9T. The films are colorless.

Solution No. 2:

Sulfuric acid 18% solution

Temperature 80ºС, current density 0.5 A/dm2.

Processing time up to 8 hours.

The film turns out black. Film thickness is about 2.5 microns.

In addition, to protect against corrosion, chemically resistant paint and varnish coatings are used, the application of which requires the use of thick oxide films (20 - 40 microns) with increased adsorption properties.

An increase in adsorption capacity is achieved by increasing the thickness of the oxide film to 20 - 40 microns. To do this, use an electrolyte from a mixture of acids.

Composition of the electrolyte for obtaining thick films, g/l:

Sulfuric acid H2SO4 350 – 400

Hydrochloric acid HCl 60 – 65

Electrochemical oxidation of titanium is carried out at 40 – 50ºС; The current density is increased stepwise every 2 - 3 minutes by 0.5 A/dm2 to the breakdown voltage, after which the current density is set to 2 - 4 A/dm2, at which electrolysis is continued until a film of the required thickness is obtained.

The friction properties of titanium parts are improved if oxide films with a thickness of 0.2 - 0.3 microns are applied to their surface.

Electrolyte composition for producing thin films:

5% solution of oxalic acid.

Electrolysis is carried out at 18 – 25°C for 60 minutes. The anodic current density at the beginning of the titanium oxidation process is set to 1 - 1.5 A/dm2 and maintained constant for 5 - 10 minutes, the voltage on the bath during this time increases to 100 - 120 V. Subsequently, the current density decreases to 0.2 - 0.3 A/dm2. The use of colloidal graphite lubricant further increases the wear resistance of the oxidized surface.

Decorative anodizing of titanium and its alloys makes it possible to obtain various interference-colored oxide films (brown-yellow, blue, cyan, various shades of yellow, including pink, crimson, and also various shades of green). The decisive influence on the color of the film is exerted by the voltage during anodizing titanium and the composition of the alloy (see “Titanium coating. Part 1.”).

Decorative anodizing of titanium.

When processing the VT-5 alloy in a 15% H2SO4 solution with increasing temperature and voltage on the bath, the color of the formed films changes from light brown to purple. An increase in the duration of electrolysis also affects the color of the films (see “Passivation of metals”).

A lesser dependence of the color of oxide films on temperature is observed when chromium anhydride is added to the electrolyte.

Composition of electrolyte for stable coloring of titanium, g/l:

Chromic anhydride CrO3 140

Sulfuric acid H2SO4 4

The color of the film in this case changes only with the duration of electrolysis at a constant voltage or with the magnitude of the applied voltage.

Thus, when treating titanium VT1-0 for 15 minutes and increasing the voltage from 5 to 50 V, the color of the film is first pale brown, then bluish-violet and then golden yellow. At a constant voltage of 50 V and increasing the duration of electrolysis from 1 to 15 minutes, the color of the film changes from light blue to golden yellow.

Anodized products can serve for many years without changing their decorative properties. Anodic corrosion protection is so effective that it can protect parts from the most aggressive influences.

For questions regarding titanium oxidation technology, please contact us!

Attention! Electroplating training course! Find out more

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Source: https://stanki-info.com/anodirovanie-titana-v-domashnih-usloviyah/

Anodizing at home - methods and technology

Many people associate the beautiful and incomprehensible word “anodizing” with complex physical and chemical technologies, laboratory conditions and other scientific paraphernalia. Few people know that this useful and simple process can be carried out using improvised means: it is possible to anodize titanium and other metals even at home. But what is it, and why is it needed for metal?

The name anodization is a process that occurs when using an electrolyte and electric current of various sizes and allows you to obtain a durable oxide foam on the product, which increases the strength of steel and provides protection against corrosion. Strength and mechanical characteristics vary depending on the composition of the metal, the density and type of electrolyte, the magnitude of the anodic and cathodic effects, calculated using special equations.

The protective coating itself is not applied, but is formed from the iron itself during an electrochemical reaction. The technology used at home looks schematically like this:

Scheme of the anodizing process at home

1. Electrolyte is poured into a dielectric (non-conducting) container.
2. A power supply is taken that can provide the required DC voltage at the output (this can be a battery or several batteries connected in electronic circuits).
3. The “+” clamp is connected to the object being processed, and the object is immersed in a container with the solution.
4. The “–” clamp is attached to a lead or stainless steel plate and is also lowered into the liquid.
5. An electric current of the required magnitude is connected, according to the electrochemical equation. Thanks to it, oxygen begins to be released on the surface of the product, promoting the formation of a durable protective film.

Anodic oxidation (anodizing) of various metals, carried out at home, is, of course, much inferior to that carried out using industrial equipment. But, nevertheless, it can provide the product with a number of advantages:

1. Increase resistance to corrosion - due to the fact that the oxide film prevents moisture from penetrating the metal base, providing reliable protection. The use of this process on quickly rusting household items or disks and parts of household appliances can significantly extend their service life.
2. Increase the strength of metal and steel: the oxidized coating is much more resistant to mechanical and chemical damage.
3. Dishes treated in this way are non-toxic, resistant to prolonged heating, and food does not burn on them.
4. After anodizing treatment, metal products acquire dielectric properties (they do not conduct current at all or almost not).
5. Possibility of electroplating of another metal (chrome, titanium). Made with your own hands, it can significantly increase the mechanical strength characteristics or improve the decorative qualities (gold plating).

In addition, the process allows for decoration. You can do color anodic oxidation. This result can be obtained by changing the equations of the applied current and the density of the electrolyte (this is possible when anodizing titanium and other hard materials) or by using paint (more often for aluminum and other soft metals, but this process is also used on hard substrates). Objects painted in this way have a more even and deeper color.

The industrial method provides higher coating strength, the ability to carry out deep anodizing with the simultaneous application of cathodic electrochemical foam, which provides additional protection against corrosion. But even anodic-cathode treatment carried out at home will help make disks or other parts of moving mechanisms more durable and wear-resistant.

Different ways

There are two ways to carry out the process of oxidizing steel at home. Each of them has its own disadvantages and advantages .

Warm method

The easiest process to do it yourself. It runs successfully at room temperature, when using organic paint, and allows you to create amazingly beautiful things. For this purpose, you can use both ready-made paints and pharmacy dyes (green paint, iodine, manganese).

Hard anodizing cannot be achieved using this technology; the oxide foam is weak, provides poor protection against corrosion, and is easily damaged. But, if you paint the surface after this technique, the adhesion (adhesion) of the coating to the base will be very high, nitro enamels or other paints will adhere firmly, will not peel off, and will provide a high degree of protection against corrosion.

Cold method

This technique, when carried out at home, requires careful control of temperature, allowing it to fluctuate from –10 to +10°C (the optimal temperature for carrying out an electrochemical reaction according to the equation is 0°C).

It is at this temperature regime that anodic and cathodic surface treatment occurs most fully, slowly creating a durable protective oxide film.

This allows the home craftsman to carry out hard anodizing with his own hands, providing the steel with maximum protection against corrosion.

Using this method, you can do electroplating by applying copper, chromium or gold to the product, calculating the current strength using special equations. After such treatment, it is very difficult to damage the steel part or discs. Corrosion protection is effective for many years, even in contact with sea water, and can be used to extend the life of diving equipment.

A small disadvantage is that the paint does not adhere to such a surface. To give color to the metal, the sputtering method (copper, gold) or electrochemical color change under the influence of electric current is used (the current strength and density of the electrolyte are calculated using a special equation).

Anodic oxidation technology

The whole process, carried out with your own hands, can be divided into stages:

1. The surfaces of disks and other metal parts are well cleaned of dirt, washed, and polished.
2. Degreasing is carried out with white spirit or acetone.
3. The required time is maintained in the alkaline solution (it is calculated by the equation based on the structure of the material).
4. After this, the disks or other metal products are immersed in an electrolyte, where the anodic and cathodic reaction of growing an oxide film is carried out.
5. If the product was cold processed, then after removing it from the container it should be thoroughly rinsed from acid and dried. After completion of this process, it is provided with long-term reliable protection against corrosion.
6. During the thermal process, the film will be porous, soft, requiring additional strengthening, carried out by dipping in clean boiling water or by exposure to hot steam. Then you need to rinse it well.

Types of electrolytes

At home, not only industrial chemical acid solutions are used, but also simple products that can be found in any kitchen:

1. When anodizing titanium, you can take sodium chloride, sulfuric or phosphoric acid.
2. For aluminum, oxalic, chromic or sulfuric acids are used.
3. Instead of acids, you can use table salt and baking soda for anodic and cathodic treatment of disks or other steel objects. You can make the necessary electrolyte by mixing 9 parts of a concentrated soda solution with one part of saline.

The exposure time of disks, plates, and other metal objects in an electrolyte container under current is calculated according to the equation, based on physical and chemical parameters.

Dangerous moments

When using acids as electrolytes, safety precautions must be strictly observed. Neglecting them can lead to accidents:

1. In case of contact with skin, due to the fact that the drug is diluted, minor burns are possible. But such a concentration is dangerous for the eyes, so you should not neglect protective glasses and gloves.
2. Under the influence of current, oxygen and hydrogen vapors are released, which, when mixed, form an explosive gas. When working in a poorly ventilated area, you can get an explosion from any spark, which can be fatal.

By following safety precautions and the stages of technological processing, you can get durable, beautiful things: chrome plating car wheels, creating gold-look jewelry, adding strength to parts of household mechanisms, depending on the technologies used.

Source: https://kraska.guru/specmaterialy/drugie-pokrytiya/anodirovanie-v-domashnix-usloviyax.html

Anodized coating: what is it, where is it used, how is it made

Anodizing is an electrolytic process that is used to increase the thickness of the layer of natural oxides on the surface of products. This technology got its name because the material being processed is used as an anode in an electrolyte. As a result of this operation, the material's resistance to corrosion and wear increases, and the surface is prepared for the use of primer and paint.

The application of additional protective layers after anodizing the metal is carried out at a much higher quality compared to the original material. The anodized coating itself, depending on the method of its application, can be porous, easily absorbing dyes, or thin and transparent, emphasizing the structure of the original material and reflecting light well. The formed protective film is a dielectric, that is, it does not conduct electric current.

Why is this done?

Anodized coating is used where it is necessary to provide protection against corrosion and avoid increased wear in the contacting parts of mechanisms and devices. Among other methods of surface protection of metals, this technology is one of the cheapest and most reliable.

The most common use of anodizing is to protect aluminum and its alloys. As is known, this metal, having such unique properties as a combination of lightness and strength, has an increased susceptibility to corrosion.

This technology has been developed for a number of other non-ferrous metals: titanium, magnesium, zinc, zirconium and tantalum.

The process under study, in addition to changing the microscopic texture on the surface, also changes the crystal structure of the metal at the interface with the protective film. However, with a large thickness of the anodized coating, the protective layer itself, as a rule, has significant porosity. Therefore, to achieve corrosion resistance of the material, additional sealing is required.

At the same time, a thick layer provides increased wear resistance, much greater compared to paints or other coatings, such as spraying. As the strength of the surface increases, it becomes more brittle, that is, more susceptible to cracking from thermal and chemical influences, as well as from impacts.

Cracks in the anodized coating during stamping are by no means a rare occurrence, and the developed recommendations do not always help here.

Invention

The first documented use of anodizing occurred in 1923 in England to protect seaplane parts from corrosion. Initially, chromic acid was used. Later, oxalic acid was used in Japan, but today in most cases, classic sulfuric acid is used in the electrolyte to create an anodized coating, which significantly reduces the cost of the process. Technology is constantly being improved and developed.

Anodized coating is done to improve corrosion resistance and prepare for painting. And also, depending on the technology used - either to increase roughness or to create a smooth surface.

At the same time, anodizing in itself is not capable of significantly increasing the strength of products made from this metal.

When aluminum comes into contact with air or any other gas containing oxygen, the metal naturally forms an oxide layer 2-3 nm thick on its surface, and on alloys its value reaches 5-15 nm.

The thickness of the anodized aluminum coating is 15-20 microns, that is, a difference of two orders of magnitude (1 micron is equal to 1000 nm). Moreover, this created layer is distributed in equal parts, relatively speaking, inside and outside the surface, that is, it increases the thickness of the part by ½ the size of the protective layer.

Although anodizing produces a dense and uniform coating, microscopic cracks in the coating can lead to corrosion. In addition, the surface protective layer itself is subject to chemical decomposition due to exposure to an environment with high acidity levels.

To combat this phenomenon, technologies are used that reduce the number of microcracks and introduce more stable chemical elements into the oxide composition.

Application

Processed materials are used very widely. For example, in aviation, many structural elements contain aluminum alloys under study, and the situation is the same in shipbuilding. The dielectric properties of anodized coating predetermined its use in electrical products.

Products made from processed material can be found in various household appliances, including players, flashlights, cameras, and smartphones. In everyday life, anodized iron coating is used, or rather, its soles, which significantly improves its consumer properties. When cooking, you can use special Teflon coatings to prevent food from burning.

Usually such kitchen utensils are quite expensive. However, an uncoated, anodized aluminum frying pan can provide a solution to the same problem. At the same time, with less money spent. In construction, anodized profiles are used for installation of windows and other needs.

In addition, multi-colored parts attract the attention of designers and artists, and they are used in various cultural and art objects around the world, as well as in the manufacture of jewelry.

Technology

To carry out work on an industrial scale, special galvanic workshops and production facilities are created, which are considered “dirty” and harmful to human health. Therefore, recommendations for carrying out the process at home, advertised in some sources, should be taken with extreme caution, despite the apparent simplicity of the technologies described.

An anodized coating can be created in several ways, but the general principle and sequence of work remain classic.

In this case, the strength and mechanical properties of the resulting material depend on the original metal itself, the characteristics of the cathode, the current strength and the composition of the electrolyte used.

It must be emphasized that as a result of the procedure, no additional substances are applied to the surface, and the protective layer is formed by transforming the original material itself. The essence of galvanics is the effect of electric current on chemical reactions. The whole process is divided into three main stages.

First stage - preparation

At this stage, the product undergoes thorough cleaning. The surface is degreased and polished. After which the so-called etching occurs. It is carried out by placing the product in an alkaline solution and then moving it into an acidic solution. These procedures are completed by washing, during which it is extremely important to remove all chemical residues, including hard-to-reach areas. The final result largely depends on the quality of the first stage.

Second stage – electrochemistry

At this stage, the anodized aluminum coating is actually created. The carefully prepared workpiece is hung on brackets and lowered into a bath of electrolyte, positioned between two cathodes. For aluminum and its alloys, cathodes made of lead are used.

Typically, the electrolyte contains sulfuric acid, but other acids can also be used, for example, oxalic, chromic, depending on the future purpose of the processed part.

Oxalic acid is used to create insulating coatings of different colors, chromic acid is used to process parts that have a complex geometric shape with small diameter holes.

The time required to create a protective coating depends on the temperature of the electrolyte and the current strength. The higher the temperature and lower the current, the faster the process. However, in this case the surface film turns out to be quite porous and soft.

To obtain a hard and dense surface, low temperatures and high current densities are required. For sulfuric acid electrolyte, the temperature range is from 0 to 50 degrees, and the specific current strength is from 1 to 3 Amperes per square decimeter.

All parameters for this procedure have been worked out for years and are contained in the relevant instructions and standards.

Third stage - consolidation

After electrolysis is completed, the product with an anodized coating is fixed, that is, the pores in the protective film are closed. This can be done by placing the treated surface in water or in a special solution. Before this stage, effective painting of the part is possible, since the presence of pores will ensure good absorption of the dye.

Development of anodizing technologies

To obtain a super-strong oxide film on the surface of aluminum, a method was developed using a complex composition of various electrolytes in a certain proportion in combination with a gradual increase in electric current density. A kind of “cocktail” of sulfuric, tartaric, oxalic, citric and boric acids is used, and the current strength gradually increases fivefold in the process. Due to this effect, the structure of the porous cell of the protective oxide layer changes.

Separately, mention should be made of technologies for changing the color of an anodized object, which can be done in different ways. The simplest is to place the part in a solution with hot dye immediately after the anodizing procedure, that is, before the third stage of the process.

The dyeing process using additives directly into the electrolyte is somewhat more complicated.

Additives are usually salts of various metals or organic acids, which make it possible to obtain a wide variety of colors - from absolutely black to almost any color from the palette.

Source: https://FB.ru/article/474539/anodirovannoe-pokryitie-chto-eto-gde-primenyaetsya-kak-izgotavlivaetsya

Anodizing steel at home

Anodizing a metal refers to the procedure of growing an oxide film using anodic oxidation. This procedure can be carried out for almost any metal.

But most often we are talking about steel, aluminum and non-ferrous metals (mainly titanium and tantalum). In turn, anodizing copper and iron turns out to be very difficult. This is due to the fact that the indicated metals form not one stable oxide, but two.

This negatively affects adhesion and significantly increases the risk of cracking of the oxide film.

Anodized aluminum - what is it, cold and warm anodizing technology

Modern devices made of metal are very different from those made 30-50 years ago. They have become lightweight, resistant to harmful influences, and minimally dangerous to life. Anodized aluminum occupies one of the leading places among the metals that are used for the manufacture of such devices.

Anodized aluminum has long and firmly taken the place of steel and cast iron where, in addition to strength and resistance to external influences, other main qualities are required - lightness and ductility.

It is much lighter than steel, so it has successfully replaced it in tens of thousands of products used in a variety of fields - industry, medicine, tourism, sports.

With the advent of anodizing technology, the remarkable properties of aluminum were supplemented by the results of chemical modification - high corrosion resistance and resistance to mechanical stress.

Some features

The process under study, in addition to changing the microscopic texture on the surface, also changes the crystal structure of the metal at the interface with the protective film. However, with a large thickness of the anodized coating, the protective layer itself, as a rule, has significant porosity. Therefore, to achieve corrosion resistance of the material, additional sealing is required.

At the same time, a thick layer provides increased wear resistance, much greater compared to paints or other coatings, such as spraying. As the strength of the surface increases, it becomes more brittle, that is, more susceptible to cracking from thermal and chemical influences, as well as from impacts.

Cracks in the anodized coating during stamping are by no means a rare occurrence, and the developed recommendations do not always help here.

Decorative materials

The anodized aluminum coating has a rather interesting structure. The outer 35-50 micron films are a microporous, sponge-like surface with very narrow and deep pores.

Even a small amount of dye penetrates deeply into anodized aluminum, turning it into a very durable and at the same time bright coating. Colorless microcrystals refract the light falling on the anodized coating, as a result of which the colors become bright and saturated.

The applied paint coating does not fade or lose its intensity.

Most modern paints and varnishes with an iridescent effect are made by adding microscopic flakes coated with oxidized aluminum. The thinnest film of anodized metal ensures high resistance of the filler to ultraviolet radiation and organic solvents, so the paint does not lose saturation for decades.

The popularity of coatings has increased so much that metal is sprayed onto steel and even cast iron structural parts for subsequent oxidation and anodized protection.

Instead of unsafe zinc coating or very expensive alloy steels, anodized aluminum is widely used today.

For example, a metal facade made of double-glazed windows of a multi-story shopping center would have to be repaired within five years, but with anodized aluminum frames the structure could last for several decades.

Crystalline metal oxide coatings have seriously displaced the most resistant powder and ceramic paints, which were previously widely used to protect facades and structural elements made of aluminum alloys.

Aluminum

Anodized coating is done to improve corrosion resistance and prepare for painting. And also, depending on the technology used - either to increase roughness or to create a smooth surface.

At the same time, anodizing in itself is not capable of significantly increasing the strength of products made from this metal.

When aluminum comes into contact with air or any other gas containing oxygen, the metal naturally forms an oxide layer 2-3 nm thick on its surface, and on alloys its value reaches 5-15 nm.

The thickness of the anodized aluminum coating is 15-20 microns, that is, a difference of two orders of magnitude (1 micron is equal to 1000 nm). Moreover, this created layer is distributed in equal parts, relatively speaking, inside and outside the surface, that is, it increases the thickness of the part by ½ the size of the protective layer.

Although anodizing produces a dense and uniform coating, microscopic cracks in the coating can lead to corrosion. In addition, the surface protective layer itself is subject to chemical decomposition due to exposure to an environment with high acidity levels.

To combat this phenomenon, technologies are used that reduce the number of microcracks and introduce more stable chemical elements into the oxide composition.

Etching a metal surface

Pickling means lightly etching a metal surface. This treatment is necessary to remove a thin film of oxides from the metal that interferes with the application of a new coating.

Picking of steel products is carried out with a solution of sulfuric acid, 80 ml of which is diluted in 100 ml of water with the addition of 2-3 g of chromium. The resulting composition is applied for 20 seconds at room temperature.

An alternative is anodic pickling in an electrolyte consisting of 150 g of chromium, 0.5 ml of sulfuric acid and 1 liter of water.

Special anodized aluminum films

In addition to high decorative qualities, anodized aluminum films have a number of very useful properties. For example, high hardness and wear resistance. The microcrystalline structure of corundum is practically not afraid of any abrasive. Sand and cement dust, and even metal carbides and silicides are not able to significantly damage the corundum protection.

Therefore, anodized parts cannot be cleaned with sandpaper or polishing or grinding paste. A thick layer of crystalline Al2O3 on the surface of rubbing parts increases the service life of any mechanism by two to three times. Protection made of oxidized aluminum is used for high-temperature painting of wheel rims, suspension elements of quarry machines and long-haul equipment.

Application of anodized aluminum coating:

• Does not degrade under the influence of frost, heat, ultraviolet radiation or chemically active substances, withstands direct contact with acids, alkalis, and organic solvents;
• Does not generate dust and does not wear out during repeated washing, cleaning, or under abrasive loads;
• There is no filamentary or gaseous form of corrosion; if the anodized aluminum layer is manufactured in compliance with the technology, then the service life of the coating can easily reach 60-80 years.

The second interesting quality of anodized aluminum film is low thermal conductivity. The processed metal is used to make foundry molds for casting copper alloys, despite the fact that the temperature of aluminum is several hundred degrees lower than that of copper. A thin, just a couple of millimeters oxidized coating reliably protects the aluminum mold from overheated liquid copper.

Source: https://instanko.ru/drugoe/anodirovannyj-alyuminij.html

Anodizing titanium and titanium alloys

The “ANODIZING TITANIUM” kit is used to form interference-colored anodic films on titanium and titanium alloys that retain the gloss of the original surface and have high light resistance, corrosion resistance and high anti-friction properties. The kit "ANODIZING TITANIUM" includes all the necessary reagents used for preparing the surface and carrying out the process of anodic oxidation (anodizing) of titanium and titanium alloys.

Using the “ANODIZING TITANIUM” kit allows you to obtain on a titanium surface, depending on the voltage in the bath, anode films of various colors and shades (brown, purple, blue, cyan, orange, yellow, turquoise, green, pink, crimson, etc. .). The differently colored sections of oxide films obtained on titanium alloys do not chemically interact with each other, have blurred color transitions and do not increase surface roughness.

Color anodizing of titanium and titanium alloys is used for marking products, for decorative finishing and giving titanium products various colors and shades, to increase corrosion, anti-friction properties, etc.

Process stages:

CHEMICAL DEGREASING → ETCHING → ACTIVATION → ANODIC OXIDATION

ANODIZING TITANIUM AND TITANIUM ALLOYS
ANODIZING COST	COST OF TITANIUM ANODIZING
Moscow, Saint Petersburg	15 l kit	30 l kit	50 l kit
40-70 rub./dm2	40-70 rub./dm2	~ 10 rub./dm2	~ 7.5 rub./dm2	~ 6 rub./dm2

Using the “ANODIC ALUMINUM OXIDATION” kit for 15 liters, with periodic adjustments, you can anodize parts with an area of ​​30-35 square meters. meters

Need to purchase

Source: https://impgold.ru/electroplating/conversion/anodizing_titan/