How to Anodize Aluminum at Home

Anodizing aluminum at home

The essence of the anodizing process is the build-up of an oxide coating, which on aluminum and its alloys performs a protective function against environmental influences. Another name is anodic oxidation. In addition, oxidation is used to improve the aesthetic appearance of products.

Surface defects are eliminated - small scratches, small chips. You can imitate coating with precious metals or increase adhesive properties. The coating can be applied not only at work, but also at home.

Anodizing aluminum at home is very popular among DIYers. In products subjected to anodic oxidation, the durability of the protective coating increases.

Aluminum anodizing

General information about anodizing technology

Aluminum anodizing technology is similar to galvanic processing. The deposition of solution oxide ions on the workpiece occurs in a liquid electrolyte at high or low temperatures. The use of a heated solution is possible in industrial installations, where it is possible to carefully control and regulate voltage and current in automatic mode.

At home, they usually use the cold method. This method is quite simple, does not require constant monitoring, and the equipment and consumables are available. To prepare the solution, you can use the electrolyte used in lead car batteries. It is sold in every auto store.

The high strength of the protective oxide film depends on its thickness, which is obtained at home by processing in a cold solution. The increase is made by stepwise regulation of the operating current.

The result of anodizing aluminumBlack anodizing aluminum

Oxidizing aluminum black is referred to as color anodizing. Black color is obtained in two stages. First, a colorless film is applied electrolytically, and then the workpiece is placed in a saline solution of acids. Depending on the acid, the color can range from pale brass to deep black. Black aluminum is widely used in construction and decoration.

Preparatory process

To obtain a smooth surface, the workpiece must be polished at the preparation stage. Using a felt or other polishing wheel, scratches are removed and large pores are tightened. The absence of micro-irregularities reduces the likelihood of burnouts. The anodic film is not able to hide external defects.

Before anodizing aluminum, it is necessary to determine the dimensions of the parts to be processed. The resulting layer is 50 microns thick, so it will be impossible to screw a nut onto the treated thread. If the parts are connected using a fit, then do not forget that after anodizing the parts cannot be ground.

Carrying out anodizing at home

To carry out the process, containers are needed. Containers for anodizing must correspond to the dimensions of the parts, and be slightly larger. Therefore, they usually use several baths. The material of the containers is aluminum. But if the products are small, then plastic containers are suitable. Only aluminum sheets need to be laid on the bottom and along the walls. This is necessary to create a current of uniform density throughout the entire volume.

The electrolyte needs to be insulated from external heat. When heating it will have to be changed. To prevent heating, the outside of the container is covered with a layer of thermal insulation. It can be covered with polystyrene foam up to 50 mm thick or, placed in a box, the free space can be filled with polyurethane foam.

A sulfuric acid solution is prepared by diluting the electrolyte for car batteries with distilled water in proportions of one to one. By purchasing a canister with a capacity of 5 liters, you can get 10 liters of solution.

Mixing, when water is added to the acid, is accompanied by abundant heat, and it literally boils and splashes. Therefore, for safety reasons, sulfuric acid is poured into a container of water.

Before anodizing aluminum begins, it is subjected to chemical preparation. Chemical preparation is a degreasing process. In industrial conditions, treatment is carried out with caustic soda or potassium. But at home it is better to use laundry soap. A toothbrush and soap solution can easily remove dirt from the surface. After that, the workpieces are first washed with warm water, and then with cold water.

An alternative to laundry soap is washing powder. After dissolving it in a closed plastic container and placing the parts to be processed there, shake vigorously. Then the parts are washed and dried with a stream of hot air. The active oxygen contained in the washing powder protects fat-free products, even if handled with bare hands.

Electrolyte preparation

Acid solutions are considered unsafe reagents, so to anodize aluminum at home, they resort to a different type of solution. To prepare it, use salt and soda, which you always have on hand.

To prepare the electrolyte, take two plastic containers. They are filled with salt and soda compositions, observing the proportion: per serving of salt or soda 9 servings of distilled water.

Anodizing at home

After dissolving the components, the solution is kept to allow undissolved particles to settle to the bottom. When pouring into a container for anodizing, it must be strained.

Aluminum anodizing methods

Several methods have been developed for processing aluminum alloys, but the chemical method in an electrolyte environment has found widespread use. Acids are used to obtain a solution:

• sulfur;
• chrome;
• oxaline;
• sulfosalicylic acid.

To impart additional properties, salts or organic acids are added to the solution. At home, sulfuric acid is mainly used, but when processing parts with complex configurations, it is preferable to use chromic acid.

The process occurs at temperatures from 0°C to 50°C. At low temperatures, a hard coating forms on the surface of aluminum. As the temperature rises, the process proceeds much faster, but the coating is highly soft and porous.

Aluminum hard anodizing technology

In addition to the chemical method, in some cases the following methods of aluminum anodization are used:

• microarc;
• color:
  1. adsorption;
  2. immersion in electrolyte;
  3. dipping into a dye solution;
  4. electroplating;

• interference;
• integral.

Warm anodizing

The warm anodizing method is used to obtain a base for painting. The coating is porous, but due to this it has high adhesion. Epoxy paint applied on top will reliably protect the aluminum from external influences.

The disadvantage is the low mechanical strength and corrosion resistance of the coating. It is destroyed upon contact with sea water and active metals. This method can be done at home.

The process takes place at room temperature or higher (no more than 50°C). After degreasing, the workpieces are mounted on a suspension that holds them in an electrolyte solution.

Anodizing continues until a milky coating appears on the surface. After removing the stress, the workpieces are washed in cold water. The parts are then painted. They are dyed by placing them in a container of hot dye. After that, the obtained result is consolidated for 1 hour.

Methods for color anodizing of aluminum

Cold technology

To anodize aluminum you need:

• power supply 12 V (battery, stabilizer);
• aluminum wires;
• rheostat;
• ammeter;
• containers for solutions.

Cold technology is different in that the growth of the anodized coating on the metal side proceeds at a faster rate than its dissolution on the outside.

First, the preparatory work described above is carried out. Then the parts need to be secured. It should not be forgotten that a film does not form under the fastening element. And suspended workpieces, when lowered into the container, should not touch the walls and bottom.

The anode is connected to the parts from the power source, and the cathode is connected to the capacitance. The current density is selected within the range of 1.6-4 A/dm2. Recommended values ​​2-2.2 A/dm2. At small values, the process will proceed more slowly, and at large values, a breakdown of the circuit may occur and the coating will begin to collapse.

It is not recommended that the electrolyte temperature rise above 5°C. When anodizing, the electrolyte does not heat up evenly. It is warmer in the center than in the corners of the container, so constant stirring is necessary.

The duration of anodizing using the cold method is about half an hour for small elements. For large parts, the duration may be 60-90 minutes. The end of the process is indicated by a changed color on the surface of the aluminum product. After disconnecting the wires, the part is washed.

Consolidate the result

The quality of aluminum anodization depends on the final stage - fixing the coating. To do this, after coating and washing, the parts are placed in a manganese solution for a quarter of an hour. After removal, it is necessary to rinse the parts under hot and cold water to remove any remaining solution from the pores.

Before staining, it is necessary to plug the microscopic pores on the film. Why the products are boiled in distilled water for 30-40 minutes.

Source: https://stankiexpert.ru/spravochnik/materialovedenie/anodirovanie-alyuminiya-v-domashnikh-usloviyakh.html

Aluminum anodizing technology at home - detailed instructions and details

This metal (in its pure form or its alloy) is the most convenient for various kinds of crafts, which is why it is popular among “home craftsmen.” Despite many advantages, aluminum also has a significant drawback - it quickly reacts with air (oxidizes), which leads to the formation of a kind of coating that complicates the process of painting workpieces. And their “pristine” appearance suits few people because of its unattractiveness.

Before considering the process of anodizing aluminum, you should understand why it is carried out. After all, during oxidation, a thin film appears on the surface of the metal, which also serves as a protection. The thing is that it is fragile and quite easily damaged.

Therefore, the meaning of the described process is to strengthen (strengthen) it. In this regard, anodizing is similar to such a no less well-known process as bluing using the oxidation method (you can read about this here). Therefore, this technology is also called anodic oxidation.

It applies not only to aluminum, but also to some other metals. For example, magnesium, titanium.

What does anodizing do?

• Strengthens the surface layer.
• Makes base defects invisible in the form of scratches and pinhole damage. In other words, it “smoothes” the metal and makes it uniform.
• Paint adheres to aluminum much better and more evenly.
• The appearance of the parts is made more attractive.
• The ability to give the metal a different shade and imitate silver, gold or, for example, pearls. Although the use of aniline dyes significantly expands the spectrum.

Cold anodizing

The most commonly used technique, especially since this method does not present any great difficulties. There is also “warm” processing of aluminum, but this technology is less effective and has not been used recently, especially in everyday life.

Advantages

• The possibility of obtaining a sufficiently thick surface layer, which is achieved by different rates of growth and dissolution of the oxide film, respectively, on its inner and outer sides. The peculiarity of the technique is that the process is carried out in the temperature range from – 10 to +10 ºС. Hence its name
• High strength of this coating.
• Increasing the anti-corrosion resistance of metal.

Flaws

He is alone, and quite relative. Further coating with organic-based dyes becomes quite difficult. The material, depending on the structural composition (if we are talking about the alloy or the characteristics of aluminum itself), is naturally colored during the anodizing process. The shade can be anything - from olive (with an admixture of “greens”) to dark (gray or black).

What you will need

• Baths. Made of aluminum - for anodizing; glass or plastic - 2 pieces - for preparing solutions.
• Connecting wires (also aluminum).

Source: https://ismith.ru/metalworking/anodirovanie-alyuminiya/

Anodizing aluminum: what is it?

As already mentioned at the very beginning, aluminum, when interacting with oxygen in the air, oxidizes. An oxide film forms on its surface, which is very unstable to mechanical damage. To secure this film and protect it from abrasion, the aluminum is anodized.

How does the property of aluminum parts change after anodizing? That's how:

• the top layer of metal is strengthened;
• visual and tactile alignment of small errors in the metal surface (scratches, pinhole damage, etc.) occurs;
• the process of applying coloring matter to an aluminum workpiece is improved;
• the part takes on a more presentable appearance;
• it becomes possible to imitate various metals (silver, platinum, gold and even pearls).

Hard anodizing of aluminum: advantages and disadvantages

Anodizing aluminum at home can be done in two ways: hard (cold) and warm. The latter, due to its complexity, is practically not used at home, but hard anodizing has become widespread among craftsmen.

This process has its advantages and disadvantages. The first include such as obtaining a thick protective layer that has good strength characteristics, as well as the formation of a high-strength anti-corrosion film on the metal surface.

Among the shortcomings, one is noted: the inability to retain a uniform layer of organic-based dye on its surface. The dye applies unevenly and is not durable. However, during the process of hard anodizing, the workpiece itself is painted in natural colors from greenish, through yellowish-brown to deep gray.

What is needed for hard anodizing

Materials and equipment you will need:

Anodizing to color change

The entire process of anodizing at home can be divided into several stages. But first I would like to dwell on the process of industrial cold anodization, which occurs using a solution of sulfuric acid. As a result of this process, active gas evolution occurs, and volatile gases are explosive. That is why it is not recommended to carry out a similar process at home.

Home anodizing technology is safer. Let's talk about its main stages in more detail.

1. Preparing the necessary solutions
   For hard anodizing, two types of solution are prepared in different containers: one is saline, the other is soda, the basis for which is drinking distilled water of medium temperature (40-50 degrees). You will need nine times more soda solution than saline solution, and therefore an appropriate container is selected for it. Salt is added to warm water with constant stirring (to another soda). Saturated solutions are prepared, i.e. salt and soda are added until a precipitate begins to form. After this, the solutions must be filtered several times. Remember that the quality of anodization depends on the quality of the solutions (their transparency and purity). Before the hard anodizing process itself, the solutions are mixed in a ratio of 1 part salt and 9 parts soda.
2. We prepare the workpiece for anodizing.
   Well, everything is simple here. The workpiece must be thoroughly sanded and degreased.
3. We anodize.
   So, let's start anodizing. The parts must be placed in the bath so that they are completely immersed in the solution and do not touch the bottom or walls of the bath. Then an electric current is applied: to the bath “minus”, to the workpiece “plus”. The workpieces remain under the influence of tension in the bath until they change color. Then the current is turned off, the workpieces are removed and thoroughly washed in running water. Afterwards, the part is placed in a manganese solution, where traces of the salt-soda solution are finally removed from the surface of the part. Then we wash it again. Do you see any stains or streaks on the workpiece? So everything went well.
4. We fix the surface layer.
   As a result of anodization, a film was formed with a large number of pores that need to be closed. This is done by simply boiling in distilled water for half an hour.
5. Varnish or paint.
   To do this, place the anodized workpiece in a container with varnish or aniline paint (10%). That's it, the part is ready.

As you can see, the anodizing process at home is simple and accessible to everyone.

angor58

Source: https://nashprorab.com/anodirovanie-alyuminiya-v-domashnikh-usl/

Anodizing aluminum at home with your own hands

Each of us has come across such a definition as anodizing, which applies, in particular, to aluminum products. This metal in its pure form or its alloys are well suited for making various crafts, which is used by many home craftsmen. The metal is light in weight, has high strength and is easy to process. But most importantly, it is resistant to corrosion. Many craftsmen anodize aluminum at home.

But why is this done, since the material itself is quite durable and looks good? However, despite all the advantages, it also has weaknesses. And its main drawback is its interaction with air, resulting in an oxidation reaction. This leads to the formation of plaque, which significantly complicates the painting of products. In addition, the type of aluminum itself is far from perfect. It is for this reason that aluminum undergoes an anodizing procedure.

What is anodizing?

According to GOST standards, anodizing is called anodic oxidation. The main result of the electrochemical process of aluminum anodization is the formation of a more durable oxide coating.

The fact is that during the oxidation of the metal, a protective film is formed on its surface, which is easily damaged. The whole point of anodizing is to strengthen this film, and not to apply any coating, which usually happens when chrome or galvanizing products. The film is formed from aluminum itself.

The process is very similar to another technology - blueing of metals by oxidation. Not only aluminum products are subjected to anodization; magnesium and titanium are also subject to such protective treatment if necessary.

The need for anodization and its methods

What can anodizing aluminum do for metal at home? First of all, the ability to resist corrosion will increase significantly. A stronger oxide protective film will last a very long time and will not peel off.

In addition, there are a number of advantages that anodic oxidation technology provides:

• Smoothes the surface of aluminum products, that is, hides some defects (scratches and pinhole damage, chips, stripes) and makes the metal uniform.
• Paint coatings adhere better to such metal due to the acquisition of a matte surface.
• Anodized aluminum profiles have improved protective properties.
• Color anodizing of aluminum gives the metal more attractive features.
• Large thickness of protective film.
• Possibility for various imitation - silver, gold, pearls, etc.

When it comes to aniline dyes, there are many options. In addition, anodizing can be performed in different ways:

• cold;
• hard;
• colored.

Let's look at them briefly below.

Cold anodizing

At home, the cold method of anodizing aluminum is often used. Many companies that offer services in this area also mainly specialize in this method. The operating temperature range is from -10 to +10 degrees, which is why the technique is called cold.

Among the advantages of anodizing aluminum at home using this method is the production of a thicker protective coating, which increases resistance to corrosion.

Only processed products are difficult to process with organic paint materials. Although the metal will acquire color in any case, and the shade can be olive, grayish or black.

Hard Anodizing

The result of solid anodic oxidation is a particularly strong protective film. Largely due to this, this technology is successfully used on a huge scale:

• industry;
• aircraft manufacturing;
• automotive industry;
• construction.

A feature of hard anodizing of aluminum is the use of several electrolytes at once. In addition to the use of sulfuric acid, a number of other analogs are also involved: oxalic, sulfuric, citric, tartaric and boric. And this is only during one process in which the current density gradually increases.

The strength of the protective coating is increased due to structural changes.

Color anodizing

The essence of this method is to change the color of the metal. In this case, 4 main methods can be distinguished:

1. Adsorption - products are immersed in a special bath or in a dye solution heated to the required temperature.
2. Electrolytic (black anodizing of aluminum) - initially a colorless film is obtained, after which the aluminum products are dipped into an acidic saline solution. Black is a common color used in construction, but a slightly bronzed tint can also be achieved.
3. Interference - the technique is similar to electrolytic, but in this case a special reflective layer is created, due to which the color palette is much larger.
4. Integral - the essence of this method is to mix the electrolyte and organic salts.

As you can understand, color anodic oxidation allows you to acquire a new shade of color, depending on your preferences.

Home technology

In industry, anodizing of metals is carried out using sulfuric acid, but anodizing aluminum at home using it is extremely undesirable due to the release of a large amount of gas. Once the slightest spark is formed, sad consequences cannot be avoided. The technique itself remains unchanged, but soda is used instead of acid.

But first you should prepare the “equipment”:

• several baths;
• wiring;
• Battery or rectifier (current source);
• rheostat;
• ammeter.

Aluminum containers are needed directly for the process itself. The other two are needed for preparing solutions, for which glass or plastic products are useful.

Preparation of an alternative electrolyte

To prepare solutions for anodizing aluminum with your own hands (soda and salt), you only need warm distilled water. The components for mixing are kept in a ratio of 1 to 9 (soda or salt - water).

The solutions are mixed well, after which they need to brew. And after some time, they need to be poured into other containers, and try to prevent the ingress of soda sediment. The final result of the procedure will depend on the purity of the solution.

Before the part is processed, it must be cleaned, if necessary, the surface must be sanded and degreased. The film thickness is no more than 0.05 millimeters, so it cannot hide visible defects.

Immediately before the process, you need to mix the prepared solutions in one container.

Electrochemical process

The container in which anodizing will be carried out must completely contain the product being processed. At the same time, it should not touch the bottom of the container. Any of the convenient options is appropriate here, you just need to be smart. The fastening of the part also needs to be carefully thought out, as this may leave traces that ideally should not exist.

According to aluminum anodizing technology, the power source is connected as follows: “plus” is supplied to the part, and “minus” is supplied to the bath. The duration of the procedure is at least 30 minutes. A change in color of the product will indicate the end of the process. You can disconnect the battery (usually it is used more often) and remove the part.

The treated product is washed well, and to get rid of the remaining solution, you can keep it in potassium permanganate for some time. Afterwards, you need to rinse it again in cold and warm water (alternately) and dry it. With the right approach, the part will be distinguished by a light gray tint, evenly covered over the entire surface. There should be no stains, streaks or drips.

Final stage

It is necessary to complete the procedure, since the resulting film is characterized by the presence of micropores that are not beneficial. They need to be closed, for which the part must be boiled in distilled water for half an hour.

Upon completion and if desired, the part can be painted or coated with clear varnish. Although the metal acquires a natural color during the process, which depends on the composition of the part being processed. Typically the shades can range from green to dark, but the result is often anodized black aluminum. To give the part another desired color, the part is immersed in a solution with aniline dyes (10%).

As you can see, anodizing aluminum can be done at home, but of all the methods, only the cold method is available, since it is safer. In addition, there is practically no difference between the type of solution (soda or acid); the result will be the same in any case. The main thing is to follow the instructions.

Source: https://FB.ru/article/342753/anodirovanie-alyuminiya-v-domashnih-usloviyah-svoimi-rukami

Anodizing aluminum at home (black) - technology

Anodizing aluminum or its anodic oxidation is considered by many entrepreneurs as one of the most promising areas for processing aluminum and its alloys.

Security questions

Carrying out high-quality anodizing at home is not difficult. It is safer and more convenient to do this work on the street or balcony. During the process, you will encounter several health hazards.

Acid is a very caustic thing. Although it is in a highly diluted form and causes only mild itching when it comes into contact with the skin, if it gets into the eyes it can cause serious injuries! Therefore, it is advisable to wear safety glasses when anodizing and always have a bucket of water or a weak soda solution on hand.

During the anodizing procedure, oxygen is released at the anode and hydrogen at the cathode. After mixing these gases, they form the well-known explosive gas, which, in principle, is the same as dynamite. Therefore, when anodizing indoors, you can die from the first spark.

The essence of aluminum anodizing

Why? What is so special about this simple process from a chemical point of view? And most importantly, what is its economic benefit? Let's figure it out.

As you know, aluminum is the most common metal on Earth, and also the most in demand. The chemical and physical properties of aluminum allow it to be used almost everywhere: in mechanical engineering, aviation, space industry, electrical and thermal engineering, etc.

Aluminum in the open air quickly oxidizes and forms a protective microfilm on the surface, which makes aluminum metal products chemically more inert.

However, this natural protection is too small, so aluminum and its various alloys do not last forever: over time they easily corrode.

There are two ways to protect aluminum products, make them harder and more durable: paint them using powder paints or oxidize them, i.e. artificially create a thick film on its surface. Oxidation, in turn, is divided into two subtypes: chemical oxidation in chromium solutions and anodization itself using anodic polarization of the product in an electrolyte.

The advantages of dyeing are that the finished products are more impressive in appearance: the resulting color is smoother, brighter, there are more possible shades of dyeing, and it is easier to obtain the desired texture.

However, anodizing is much less dependent on the quality of the supplied materials, and production lines are simpler. In addition, the range of colors and shades of anodized metal products is becoming larger and larger every year.

Even iridescent anodizing is now available, creating an iridescent, shiny coating on the surface of the product.

Anodizing technology

The anodizing process can be divided into three parts:

• preparatory process;
• chemical treatment;
• consolidation

Chemical treatment

Chemical oxidation of aluminum is the treatment of metal in an electrolyte. Solutions of various acids (sulfuric, chromic, oxalic, sulfosalicylic) are used as electrolytes. Sometimes salt or organic acid is added to solutions.

The most common electrolyte is sulfuric acid. Yet this electrolyte is not used for processing products of complex shapes that have small holes or gaps. In such cases, chromic acid is preferred. But oxalic acid can significantly improve multi-colored insulating coatings.

Chemical oxidation of aluminum

The quality of the process depends on several components, including concentration, temperature and current density. High temperatures speed up anodization. Moreover, the film formed is soft and highly porous. If a hard coating is required, a lower temperature is used.

Chemical oxidation of aluminum can be carried out at temperatures from zero to plus 50 degrees Celsius. Current density can vary from 1 to 3 Amps per square decimeter. The electrolyte concentration indicator can be in the range of 10-20%.

Consolidation

After oxidation, the metal looks like a porous surface (even when using cold mode). In order for the surface to be strong enough, these pores must be blocked. This is done in one of three ways:

• dipping the product in hot fresh water;
• steam treatment;
• placing the metal in the so-called “cold solution”.

Note! If the product will be painted, the fixing process is not necessary, since the paint material will naturally fill the existing pores.

There are three types of equipment for aluminum oxidation:

• basic (baths);
• servicing (providing work);
• auxiliary (feeding products into the bath, preparing, storing, etc.).

Preparatory work

Remember that parts become larger after anodizing. The thickness of the protective anodic layer is usually 0.05 millimeters. For example, threads that were previously tightly tightened will no longer tighten at all after the anodizing process, since in this case the bolt in the nut will become 0.2 millimeters tighter. And it is almost impossible to polish anodized.

It is useful to polish the products to a mirror shine on a polishing wheel. Thus, the aesthetics of the part will greatly benefit and the likelihood of “burnout” during anodizing will be reduced. By the way, the anodic layer does not mask surface defects - they will be noticeable on the processed product.

Before galvanizing, aluminum must be thoroughly degreased. You should not keep the metal in hot caustic sodium or potassium, as is recommended in factory technologies, because the cleanliness of the surface noticeably deteriorates. It is better to use a bar of laundry soap and a toothbrush, because you will be working with small parts. First rinse the product in warm water, then in cold water.

Washing powder works very effectively: it needs to be dissolved in hot water in a plastic container. Then you should pour the products there and shake the vessel well. After washing, dry the parts thoroughly with hot air. Don’t worry about small traces of fat: after degreasing, you can pick up the product because the layer of fat from your fingers is instantly oxidized by oxygen.

Electrolyte production

The electrolyte for anodizing at home is a solution of sulfuric acid in distilled water. You can also use ordinary tap water, but if you can take distilled water, it is better to choose it, since in the first case the uniformity of the process—the distribution of current density on the surface of the part—is slightly deteriorated.

It’s stupid to make sulfuric acid yourself, but distilled water is very easy! If there is no snow or rain outside, then there will always be ice in the freezer. You can get distilled water and sulfuric acid at your local auto parts store, as these ingredients are used to service car batteries.

However, the acid is sold there in a diluted form to a density of 1.27 grams per cubic centimeter under the name “Electrolyte for a lead battery.” You need to mix this electrolyte with distilled water in a 1:1 ratio.

If you take a standard 5 liter canister of electrolyte and the same amount of water, you will end up with 10 liters of anodizing solution. This is enough for small parts, but for large parts it is worth doubling this amount.

Remember that mixing acid with water will generate a lot of heat. If you pour water into acid, it will instantly boil, splashing in your face! That is why it is recommended to pour the electrolyte into a container of water in a thin stream, stirring constantly with a glass rod. And it's better to wear safety glasses! If acid gets on clothing or skin, rinse it off immediately with a stream of water and rinse with a soda solution.

How to blacken aluminum at home

Each of us has come across such a definition as anodizing, which applies, in particular, to aluminum products. This metal in its pure form or its alloys are well suited for making various crafts, which is used by many home craftsmen. The metal is light in weight, has high strength and is easy to process. But most importantly, it is resistant to corrosion. Many craftsmen anodize aluminum at home.

But why is this done, since the material itself is quite durable and looks good? However, despite all the advantages, it also has weaknesses. And its main drawback is its interaction with air, resulting in an oxidation reaction. This leads to the formation of plaque, which significantly complicates the painting of products. In addition, the type of aluminum itself is far from perfect. It is for this reason that aluminum undergoes an anodizing procedure.

According to GOST standards, anodizing is called anodic oxidation. The main result of the electrochemical process of aluminum anodization is the formation of a more durable oxide coating.

The fact is that during the oxidation of the metal, a protective film is formed on its surface, which is easily damaged. The whole point of anodizing is to strengthen this film, and not to apply any coating, which usually happens when chrome or galvanizing products. The film is formed from aluminum itself.

The process is very similar to another technology - blueing of metals by oxidation. Not only aluminum products are subjected to anodization; magnesium and titanium are also subject to such protective treatment if necessary.

What can anodizing aluminum do for metal at home? First of all, the ability to resist corrosion will increase significantly. A stronger oxide protective film will last a very long time and will not peel off.

In addition, there are a number of advantages that anodic oxidation technology provides:

• Smoothes the surface of aluminum products, that is, hides some defects (scratches and pinhole damage, chips, stripes) and makes the metal uniform.
• Paint coatings adhere better to such metal due to the acquisition of a matte surface.
• Anodized aluminum profiles have improved protective properties.
• Color anodizing of aluminum gives the metal more attractive features.
• Large thickness of protective film.
• Possibility for various imitation - silver, gold, pearls, etc.

When it comes to aniline dyes, there are many options. In addition, anodizing can be performed in different ways:

• cold;
• hard;
• colored.

Let's look at them briefly below.

Anodizing aluminum at home

[Anodizing aluminum at home] with your own hands is necessary if you want the material to be protected from corrosion and last as long as possible.

Aluminum is very often used in home production and everyday life, so knowing how to protect it yourself without resorting to the help of specialists will be useful for everyone.

Thanks to anodization, a dense and thick oxide film appears on the metal surface, which protects it from corrosion and other negative factors of the natural environment.

Thin-layer anodizing technology, which you will learn about in this article, will help you create the most durable and resistant film.

Preparation for anodizing

Anyone can do anodizing with their own hands, but you need to take minimal precautions before starting work. It is best for the process to take place outdoors: on the street or at least on the balcony.

You also need to think about self-defense, because... During anodizing, you will be dealing with acid, and this is a chemical that can cause unpleasant itching if it comes into contact with the skin, and much more serious injuries if it gets on the mucous membrane of the eyes.

You can see the anodizing process with your own hands in the photo.

It is best to do anodizing while wearing safety glasses and prepare water or a weak soda solution in advance so that, if anything happens, you can immediately rinse the area where the acid has come into contact.

Anodizing should never be carried out indoors, because... you will be dealing with oxygen and hydrogen emissions that appear at the anode and cathode.

The result will be an electrochemical compound with properties similar to dynamite.

If you create such an electrochemical compound in a closed space, then one spark generated by the electrochemical compound will be enough to cause serious injury and even death.

Before starting work, consider the size of the parts: after the anodizing process they will increase in size by at least 0.5 mm - this is the thickness of the protective layer that is created during the process.

If before anodizing the parts are tightly screwed, then after it is finished they most likely will not be screwed at all and all the work will be in vain.

Therefore, make sure that the materials move freely before starting anodizing, so that later you do not have to start the whole work again, because. Sanding an anodized surface is practically useless.

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However, you can polish the parts using a buffing wheel until they have a mirror finish. This can be done with your own hands.

Thanks to this process, the products will look better and will also reduce the likelihood of burnout, which is not uncommon during anodizing.

In addition, the anodizing technology does not in any way affect the defects of parts - if they exist, they will remain noticeable even after the work is completed.

Galvanization is a necessary stage preceding the main work. Before doing this, the metal must be thoroughly degreased. To do this, it is better to use laundry soap and a brush.

Some people advise soaking the metal in sodium or potassium, but this can cause the surface to deteriorate. It is necessary to rinse the products alternately, first in hot and then in cold water.

You need to add washing powder to a plastic container and dissolve it in hot water, and then pour the parts into it and shake them. After washing, you need to dry the solid body of the parts under hot air.

To carry out anodizing, you will need an electrolyte, which you can make yourself. For home production, sulfuric acid is most often used, which is diluted in distilled water.

You can buy both water and acid at any auto parts store so as not to waste time making them yourself.

You just need to take into account that in stores the acid is sold diluted, so the proportions for mixing the liquid should be 1:1. The anodizing process requires about 10 liters of electrolyte for small parts and 20 for large ones.

Therefore, you will need 5 liters of solution and 5 liters of water to get the required amount.

You need to pour water into the acid gradually, in a thin stream, because... the liquid instantly heats up and with a large flow it will simply boil and begin to splash. Don't forget to stir the mixture with a glass rod and put on your glasses before working.

If acid gets on your skin or clothing, it must be removed with water, and then rinse the area with a soda solution.

Stages of work

When anodizing parts, the temperature should remain in the following range: from -10 to + 10 degrees.

If it is lower, then the voltage of the power supply will not be enough to maintain the required current strength, and if it is higher, then a hard protective coating will not form - it will be soft and colorless and will not be able to protect the metal.

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It is best to finish anodizing when the temperature has reached +5 degrees, because... There will be different temperatures in the corners of the bath and on the surface of the object, and the anodizing procedure allows you to generate a sufficient amount of heat.

In addition, the process of moving the electrolyte must be constant: it can be stirred with air, a spoon or a pump so that the temperature on the surface of the workpiece and the aluminum is approximately the same.

The temperature difference will lead to the fact that some areas of the part will overheat, and then breakdowns will appear on them or the product will be damaged.

To perform hard gold anodizing, you will need special equipment. Most often, these are several baths, in one of which aluminum parts will be processed, and the other - a small container.

You can use food containers or plastic pots for this. The walls and bottom of the bathtubs need to be covered with aluminum sheets, or a special pattern should be made from them and bent to form a container.

This is necessary to create a uniform current density on each side of the product.

The bath body must have good thermal insulation, otherwise the electrolyte will heat up too quickly, and the liquid will have to be constantly changed.

The easiest way is to create a thermal insulation layer by covering the walls with foam plastic 2-4 cm thick, or filling the gaps with construction foam.

After you have poured the electrolyte into the bath, you need to install a power supply generating current at the output. To regulate the amount of current supplied, attach a resistor to the circuit.

If the contact is good, you will see oxygen bubbles that will appear over the entire surface of the product. They are small in diameter and flow like streams of smoke.

The duration of this process depends on the speed of painting the parts - gold or another color. Painting the color will be visually noticeable, so no other devices are required.

The speed of painting gold, black and other shades depends on the size of the part: for small objects it is about 20-30 minutes, for large objects it is 60-90 minutes.

After the entire part has acquired the desired color, remove it from the container and rinse it under cold water, and then wipe it with a cotton swab dipped in a solution of potassium permanganate - this will help remove excess trace elements resulting from the reaction, but will help maintain the color gold or another.

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After removing the part, it should have a light gray color, be smooth and shiny.

Depending on the anodizing modes, products can acquire different colors: gray, dark matte, gold, etc. To further color the parts, you need to place them in an aniline dye, which will heat the part to 50-60 degrees.

Before starting color anodizing, you need to filter the solution so that stains that appear from remaining small grains of dye do not form on the surface of the parts.

To dye the products and get the desired color, 15-20 minutes is usually enough.

After the required color (black, gold, etc.) and the protective layer of the correct consistency (hard and shiny) have been obtained, you need to further fix it so that it does not peel off over time.

Since gold anodizing creates a porous structure of the material, which is not resistant to chemical influences, although it is carefully protected from mechanical influences.

The technology for closing micropores on metal can be different. The easiest way is to boil anodized parts in water on the stove for 30 minutes. For cooking, it is best to use distilled water, because... it will give the material more protective properties.

Another way: make a steam bath for the parts, in which they should also remain for at least half an hour.

The technology for working with aluminum may differ slightly, depending on the type of part and material, but in general, all stages of anodizing a material look similar.

There may be differences in the temperature of the electrolyte, however, it is recommended to follow the given figures, because otherwise, the protective properties of the material will be insufficient, or you will not get the color you needed.

If you are anodizing for gold and other colors, then it is best to choose the cold method, because in this case, the coating layer will be thicker, and the parts themselves will acquire a beautiful color: gold, black or other shades, and will also shine.

Source: https://rezhemmetall.ru/anodirovanie-alyuminiya-v-domashnix-usloviyax.html

Anodizing aluminum at home technology

The essence of the anodizing process is the build-up of an oxide coating, which on aluminum and its alloys performs a protective function against environmental influences. Another name is anodic oxidation. In addition, oxidation is used to improve the aesthetic appearance of products.

Surface defects are eliminated - small scratches, small chips. You can imitate coating with precious metals or increase adhesive properties. The coating can be applied not only at work, but also at home.

Anodizing aluminum at home is very popular among DIYers. In products subjected to anodic oxidation, the durability of the protective coating increases.

Anodizing aluminum at home: process technology:

External processing of metal alloys is widely used in various fields to provide decorative and protective properties.

Anodizing (anodic oxidation or oxidation) also allows you to endow structures and parts with special aesthetic or technical and operational qualities through the formation of a film coating.

Typically, such processes are organized in production and in the construction industry, but simplified anodization of aluminum is also possible in everyday life. At home, this process is organized using available chemical materials and appropriate technical equipment.

General information about the technology

The anodizing process consists of several technological stages, including mechanical and chemical preparation, the actual creation of the coating and, if necessary, correction and modification of the product. Primary mechanical processing is carried out with the aim of eliminating scratches, marks, dents and other defects on the surface that will not allow the operation to be performed efficiently.

In particular, color anodizing of aluminum requires ensuring maximum smoothness of the surfaces of the workpiece, which will allow it to impart a natural shine with a shimmer. Processing is carried out by grinding and polishing, but large abrasives should be avoided. The best option would be felt and felt circles.

Already at this stage, it is possible to provide elements of chemical preparation - for example, Viennese lime or the same aluminum oxide are used as polishing pastes. Sometimes chemical electropolishing is performed using special equipment.

As for direct chemical preparation, it is performed through degreasing, etching and brightening operations. Already during the anodizing process, painting or sealing can be done.

Again, in the domestic sphere, this processing method is more often used for decorative color changes. Anodizing aluminum allows you to give the workpiece light gray, black, red, blue and other shades.

A separate category of the palette is occupied by imitating colors - for example, with an aging or “bronze” effect.

Preparing the container for anodizing

Anodizing is carried out in a container with electrolyte, the preparation of which should be done separately. For large structures or parts, you need to use a bath, also made of aluminum. Small-sized workpieces are processed in containers, pots or basins, which can be made of plastic.

Sometimes containers that do not meet the characteristics are additionally covered with sheets of this metal. It is optimal if the bottom and walls are hermetically covered with an aluminum layer. This will allow the current to be evenly distributed covering all sides of the workpiece. Next, the container should be thermally insulated from the outside.

The fact is that anodizing aluminum at home does not allow you to accurately regulate the thermal conditions of the container body and its contents. Therefore, you should insulate the structure in advance using polystyrene foam 2-3 cm thick.

If you plan to regularly use anodizing, you can prepare a special bath with fixation on a profile sealed frame and filling with polyurethane foam.

At the final stage of preparing the container, a lead cathode is made, which will be connected to the bath. In this part, it must be taken into account that the area of ​​the electrical element must be twice the target area for anodizing aluminum. You can make a cathode with your own hands from sheet lead removed from the protective sheath of a thick cable. Also, small holes should be provided in this element that will allow the release of gas during processing.

Securing the part

Before starting the anodizing process, the part must be firmly fixed to the hanging fixtures for tighter electrical contact. It is recommended to use aluminum structures or titanium-based alloys with duralumin as suspension devices. The fastening itself can be done using screw or spring clamping mechanisms.

For additional insurance, aluminum tight wire is often used. Areas of the structure that will not participate in contact must be isolated. This can be done either with polyethylene tape or with acid-resistant varnish.

The second method requires additional caution, since color anodizing of aluminum at home involves the maximum exclusion of external influences on the surface of the workpiece. That is, varnish treatment must be carried out in advance with the surface completely dry.

It should also be taken into account that loose contact of the suspension system with the target material can cause overheating of the latter. This effect, in turn, will lead to the destruction of the oxide coating and a decrease in the strength of the applied film.

Optimal processing mode

The optimal temperature regime for oxidation is in the range from -10 to 10 °C. Going beyond these limits involves certain risks in terms of obtaining a high-quality color coating. Thus, low temperatures will not allow the home electrical system to maintain sufficient current for processing.

Conversely, an increase in heat will make it possible for a dense layer to form, but the film may not be so expressive in its shade. However, anodizing aluminum at home in black or light gray can also be done in an elevated temperature mode.

Another thing is that the mechanical state of the surface structure of the workpiece will differ in different areas. This occurs due to the fact that there is uneven heat distribution throughout the entire volume of the electrolyte. Attention should also be paid to the current density at the anode. It is recommended to maintain the value within the range of 1.6 - 4 Amperes per 1 dm2.

With this current supply, a densely colored, durable protective layer can be obtained. Reducing this indicator will provide a thin layer, and increasing it will promote etching of the product.

Anodizing process

By the time the process begins, the container, cathode with power supply, target part, suspension structure and electrolytic mixture must be prepared. To regulate the current, it is necessary to connect a variable resistor to the electrical circuit. The container should contain two objects - a prepared lead cathode and a workpiece. When current is applied, the process of oxygen release will begin and the part will receive an increase in the protective layer.

The effectiveness of the reaction can be judged by the intensity of the release of oxygen microbubbles, which will slowly move away from the surface of the workpiece. As for processing time, the standard aluminum anodizing technology for small elements requires 20-30 minutes. Large workpieces are processed within 30-60 minutes. When the part has acquired a dark matte color, it can be immersed in a solution of aniline dye with the desired shade.

On average, another 15-20 minutes are allotted for coloring.

Consolidation of anodizing results

When the part acquires the required color, a new layer on the surface will need to be fixed. The need for additional strengthening is due to the fact that the anodized coating has a porous structure that is easily permeable to water and air. Therefore, immediately after staining, the micropores should be closed.

The simplest method to achieve this effect is through a cooking process in distilled boiling water. This procedure should take about 30-40 minutes. But if the process of anodizing aluminum was carried out at low temperatures, then it is better to abandon this method in favor of a steam bath.

The part is kept under the intense influence of the steam generator for 30 minutes, after which it is washed and dried.

Alternative Methods

In this case, the simplest method of oxidation with a sulfuric acid electrolyte was considered. But if you need to obtain a higher-quality coating, you can also use the technology of anodizing aluminum in sulfosalicylic acid, which forms thin but dense layers of coating.

This is due to the fact that the electrolyte has minimal impact on the metal in terms of its solubility. But this effect, if necessary, can be compensated by adding the same sulfuric or oxalic acid to the active mixture. Processing in two-component sulfosalicylate media is also common.

On the contrary, thanks to a slow increase in the temperature of the anode, it makes it possible to build up thick and durable coatings while maintaining a low current.

As an alternative, we can offer the so-called cold oxidation method. In this case, the process occurs at temperatures below zero. Risks have already been noted when using borderline temperature values, but this option justifies itself when you need to get not a decorative, but a protective base on the surface.

In other words, cold anodizing of aluminum at a temperature of about -10 °C will not provide the part with a pronounced decorative shade, but will make its external structure stronger.

But, again, this method will require the use of electrical equipment that can stably maintain a current voltage of more than 12V.

Safety precautions

As already noted, special safety requirements must be observed when handling electrolyte. It is advisable to wear gloves and safety glasses. The working air environment will also pose a danger, so the process should be organized in a room with an active supply and exhaust ventilation system.

All containers with explosive and flammable mixtures must be removed from the bath and electrical equipment that provides the aluminum anodizing process. At home, it also makes sense to carry out the operation with manual fire extinguishing equipment. Special attention is paid to subsequent cleaning of equipment.

The container and auxiliary equipment should be washed in special solutions, and the remaining electrolyte should be disposed of.

Conclusion

Oxidation of metals with acids is primarily used as a processing procedure in industrial settings. But lately, ordinary people are increasingly looking at it. Why might such a coating be needed in the domestic sphere? Anodizing aluminum allows you to change the aesthetic qualities of the material, but in most cases the technology is used for practical protection purposes.

A high-quality oxidized layer on the metal surface allows to minimize corrosion processes. In the case of aluminum, these can be parts of cars, engineering equipment, roofing sheets and elements of other building structures.

There are also less complex methods of such protection, but electrochemical treatment by anodizing provides an increased degree of protection of the metal structure from external influences.

Source: https://www.syl.ru/article/347757/anodirovanie-alyuminiya-v-domashnih-usloviyah-tehnologiya-protsessa