What is metal anodizing - Metals and their processing

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.

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.

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.

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.

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.

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.

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.

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.

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 metal: description and types of coating, nuances of working at home - Machine

An attractive appearance and increased strength properties of a metal surface can be achieved by using special electrochemical reactions. One of these methods is anodizing the metal, during which a protective oxide film is formed on the surface, giving the material additional qualities.

Features of anodized

This procedure is widely used on an industrial scale; in addition, you can independently oxidize steel, aluminum or copper at home. The latter option will differ from the professional process, but it is convenient for processing small parts.

Products that have a film formed on their surface after anodizing have the following characteristics:

increased resistance to corrosion;
the strength of materials such as steel and aluminum increases;
the product becomes non-toxic;
lack of ability to conduct current;
the prepared surface is suitable for further processing using galvanic coating.

The procedure of anodizing metal is used for the production of cookware - products processed by this method do not burn on the stove and are safe for cooking. Materials with an oxide film are used in the manufacture of some tools, building materials, lighting devices, and household items. In addition, silver products are processed.

Color anodizing is widespread, which allows you to give parts a variety of decor. Products painted in this way have a more even and deeper color.

The anodized surfaces of tools and devices do not crack during use, maintaining their original appearance for a long time. In addition, the plane becomes stronger, which allows it to withstand increased loads and mechanical stress.

How does the anodizing process work?

The whole procedure consists of three stages of work: preparing the metal, its chemical treatment and fixing the coating to the surface. We propose to take a closer look at each of these phases using the example of processing a material such as aluminum:

Preparatory stage. The metal profile is cleaned mechanically, after which it is polished and degreased. This must be done so that the coating is firmly fixed to the base. Next comes the use of alkalis. The part is placed in the solution for some time for etching, after which it is transferred to an acidic liquid, where the aluminum is brightened. The final stage of anodic preparation is the complete washing of parts from residual alkali and acid.
Chemical reaction. The prepared product is placed in an electrolyte. It is a solution of acid to which a current is connected. The material to be anodized is most often treated with sulfuric acid, and its oxalic analogue is used to achieve color. A successful result is achieved with the correct temperature and current density. Hard anodizing involves the use of low temperatures, but if the goal is to obtain a soft and porous film, the performance increases.
Stage of fixing the coating. The resulting aluminum parts with the film formed on them have a porous appearance, so they need to be strengthened. Several methods are used for this: dipping the product in hot water, treating with steam or a cold solution.

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For further color painting of the product, there is no need to fix the anodizing. Existing paints and varnishes adhere perfectly to the porous surface, forming excellent adhesion to it.

It is worth noting that metals are coated with such anodizing at industrial enterprises. A particularly durable type of coating can be achieved with a hard type of procedure. This material is used in automobile production, aircraft construction and construction.

Method of procedure at home

When starting anodizing yourself at home, you must first prepare all the tools:

container for placing the product;
batteries with a capacity of 9 V (several pieces, depending on the desired result);
aluminium foil;
cable with good insulation;
electrolyte solution;
ticks.

As an experimental experience, you can try processing the bolts. The thickness of the finished coating is approximately 0.05 mm. Products must be prepared in advance. If stainless steel elements were selected, degrease and sand them in advance.

Prepare an electrolytic solution. To do this you will need sulfuric acid and distilled water. You can purchase acid for the electrolyte at auto stores that specialize in battery repair. The proportions of water and acid should be the same, but you should not use an undiluted substance.

It will take longer to achieve a black metal color than a light or bronze result.

First, etch the part in lye to prepare it. After this, place the part in a solution with electrolyte and connect the current. It is important to use a thermometer to monitor the temperature and ensure that the readings do not drop. When the level reaches the lower levels, it is necessary to end the process.

Source: https://regionvtormet.ru/beton/anodirovanie-metalla-opisanie-i-raznovidnosti-pokrytiya-nyuansy-raboty-v-domashnih-usloviyah.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:

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.
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.
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.

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 steel at home

One of the important tasks in preserving metal structures is combating the harmful effects of the environment. High humidity and the presence of chemically active elements in the air that can destroy the integrity of metal, especially steel, lead to a deterioration in such indicators as reliability and strength.

To solve this problem, finished products are coated with various types of protective coatings.

Chemical oxidation

This process involves the processing of metals with solutions, mixtures, melts of chemical elements (oxides such as chromium oxides). This oxidation allows for the so-called passivation of the metal surface. It involves the creation of an inactive (passive) formation in a metal layer close to the surface. A thin surface layer is created that protects the main part of the structure.

Technologically, this process is implemented by lowering the prepared metal part into an alkali or acid solution of a given percentage.

They keep it there for a certain time, which allows the oxidation-reduction reaction to fully occur. Then the part is thoroughly washed, subjected to natural drying, and final processing.

To create an acid bath, three types of chemically active acids are used: hydrochloric, nitric, and orthophosphoric. The acceleration of the chemical reaction is stimulated by adding manganese, potassium, and chromium compounds to the acid solution. The oxidation reaction occurs at a solution temperature in the range from 30 °C to 100 °C.

The use of solutions based on alkaline compounds allows the use of additives of sodium nitrate and manganese dioxide compounds. In this case, the solution temperature must be increased to 180 °C, and with additives up to 300 °C.

After the procedure, the part is washed and dried. Sometimes potassium bichromate is used to consolidate the chemical reaction process. To increase the shelf life of the formed film, chemical oxidation with oiling is carried out. Sometimes this process is called chemical oxidation. The final coating with oil results in a reliable anti-corrosion coating with a striking, highly decorative black color.

Anodic" oxidation

This type is called electrochemical oxidation of steel. Sometimes it is called anodic oxidation of steel. The term anodizing is also used. It is based on the chemical process of electrolysis. It can be carried out in both solid and liquid electrolytes. The prepared workpiece is placed in a container with an oxide solution.

The electrolysis reaction is possible by creating a potential difference between two elements.

The surface of the oxidized product is characterized by a positive potential. Chemically active elements with a negative potential are isolated from the solution. The interaction of oppositely polar elements is called the electrolysis reaction (in our case, anodization).

The anodization reaction can be performed at home. It is required to strictly comply with safety regulations. The reaction involves harmful reactive fluids and unsafe voltage.

The use of anodic oxidation makes it possible to create protective films of various thicknesses. The creation of thick films is possible through the use of a sulfuric acid solution.

Thin films are obtained in solutions of boric or phosphoric acid. Using anodization, you can give the surface layer of metal beautiful decorative shades. For this purpose, the process is carried out in organic acids. Oxalic acid, maleic acid, sulfosalicylic acid are used as such solutions.

Micro-arc oxidation is a special anodizing process. It makes it possible to obtain coatings with high physical and mechanical characteristics. These include: protective, insulating, decorative, heat-resistant and anti-corrosion properties. In this case, oxidation is carried out under the influence of alternating or pulsed current in special baths filled with electrolyte. Such electrolytes are weakly alkaline compounds.

Anodizing allows you to obtain a surface layer with the following properties:

reliable anti-corrosion coating;
good electrical insulators;
thin but durable surface layer;
original color scheme.

Anodizing stainless steel requires a special approach. This is due to the fact that such steel is considered a neutral (inert) alloy. Therefore, in production, when anodizing a large number of parts, a two-step procedure is used.

At the first stage, stainless steel is anodized together with another metal that is more suitable for this process. It may be nickel, copper, other metal or alloy.

At the second stage, the stainless steel itself is oxidized directly. To simplify the oxidation process, special additives, so-called passivating pastes, are being developed today. These compounds speed up the reaction process of stainless steel.

Thermal oxidation

According to the term, oxidation occurs at relatively high temperatures. The value of this indicator depends on the steel grade. For example, the process of thermal oxidation of ordinary steel occurs in special furnaces.

A temperature close to 350 °C is created inside. A class of alloy steels undergo thermal oxidation at higher temperatures. It is necessary to heat the workpiece to 700 °C. Treatment continues for one hour.

This process is called steel bluing.

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Plasma oxidation

This oxidation is carried out in an environment with a high concentration of oxygen using low-temperature plasma. Plasma is created due to discharges that occur when high- or ultra-high-frequency currents are applied.

Plasma oxidation is used to form oxidized films on fairly small surfaces.

It is mainly used in electronics and microelectronics. With its help, layers are formed on the surface of semiconductor compounds, the so-called pn junctions. Such films are used in transistors, diodes (including tunnel diodes), and integrated circuits. In addition, it is used to increase the photosensitive effect in photocathodes.

A type of plasma oxidation is oxidation using high-temperature plasma. Sometimes it is replaced by an arc discharge with an increase in temperature to 430 ° C and higher. The use of this technology can significantly improve the quality of the resulting coatings.

Laser oxidation

This technology is quite complex and requires special equipment. To carry out oxidation use:

pulsed laser radiation;
continuous radiation.

In both cases, infrared laser systems are used. Due to laser heating of the top layer of material, it is possible to obtain a fairly resistant protective film. However, this method is only applicable to a small surface area.

DIY oxidation

You can organize the process of oxidation of small metal products in your home laboratory. By strictly following the sequence of technological operations, high-quality oxidation is achieved.

The whole process should be divided into three stages:

Preparatory stage (includes preparation of the necessary equipment, reagents, and the part itself).
Direct oxidation stage.
The final stage (removing harmful traces of the chemical process).

At the preparatory stage the following work is carried out:

Rough cleaning of the surface (use a metal brush, sandpaper, polishing machine with appropriate discs).
Final mechanical polishing of the surface.
Removing grease and polishing residues. It's called decopying. It is carried out in a five percent solution of sulfuric acid. The residence time of the workpiece in the solution is one minute.
Washing the part. This procedure is carried out in warm boiled water. It is advisable to carry it out several times.
The final operation is the so-called passaging. After washing the part after processing, place clean boiled water in which laundry soap is first dissolved. This solution, together with the part, is heated and brought to a boil. The boiling procedure is continued for several minutes.

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This concludes the preliminary stage.

The main stage of oxidation consists of the following operations:

Water is poured into a neutral bowl (preferably with an enamel coating). About caustic soda is dissolved in it. The volume of a substance depends on the amount of water. It is advisable to obtain a solution of about 5 percent.
The workpiece is completely immersed in the resulting solution.
The solution with the immersed part is heated to 150 degrees. This is practically a boiling process. It lasts approximately two hours. Using the tool, the quality of the process is checked. If necessary, the time can be increased.

At the final stage, the following operations are performed on the part:

The part is removed from the reagent bath.
Place it on a flat surface and allow it to cool naturally (without forced cooling). It is advisable to create conditions that limit contact with ambient air.
Visually check the quality of the resulting oxidation. The absence of uncovered areas, the density of the formed film, the final color.

Thus, oxidation can be carried out at home. The main thing is to follow these recommendations.

Source: https://morflot.su/anodirovanie-stali-v-domashnih-uslovijah/

Why anodizing is needed

What is anodizing and why is it needed?

The essence of the phenomenon
Why is this necessary?
Features of care

You may have noticed that on expensive bicycles some parts and components are not painted or polished, but seem to be covered with some exceptionally smooth and beautiful material.

Usually these are the fork legs and the shock absorber rod, but often there are other parts, ranging from large ones, such as handlebars or rims, to every little thing, such as tuning knobs and caps. So, this unusual coating is called anodizing.

And it carries several useful functions at once.

The essence of the phenomenon

We will not go into brutal physics and other engineering jungle here. Therefore, we will describe it briefly and clearly. When we talk about anodizing, especially in a bicycle topic, we most likely mean that our part is made of aluminum. This process is also applied to other metals, but in percentage terms the undisputed leader is aluminum.

So, anodizing is a process in which the part is immersed in a bath of electrolytic solution. Cathodes are installed in the same bath. When an electric current passes through an acid solution, hydrogen is released at the cathode and oxygen at the anode. Thanks to this, an oxide layer is formed on the surface of the part, which protects it from evil and adds a whole bunch of useful properties. Since the part is the “anode” in this electrolytic process, the entire process is called “anodizing.”

There are quite a few anodizing methods and solution compositions. Depending on the chemical composition of the solution used and additional additives, the color of the coating of the finished part varies. As a rule, these are various shades of yellow, orange or brown, as well as black. However, there are special dyes for anodizing that allow you to obtain almost any color in the output.

Why is this necessary?

This is all clear, but why is all this needed in the bicycle industry? As soon as the price of a bicycle soars, using steel in it becomes a little comme il faut. Therefore, aluminum and various lightweight composite materials are used. Aluminum is lightweight and has good strength, which is why it has taken root in the cycling world. Well, after aluminum, methods for processing it came into this world.

There are three complementary purposes of anodizing in a bicycle theme.

It will be unpleasant for anyone if your favorite part suddenly becomes covered with nasty stains and simply rots over time. Anodizing, while it is intact, perfectly protects parts from this scourge. The main thing is not to forget to follow. In addition, in the case of such important parts as fork legs and shock absorber rod, damage to the anodization will entail, in addition to corrosion, oxidation and an unsightly appearance, a lot of troubles, such as, for example, oil leakage through the resulting gap.

Anti-friction properties of anodized coating.

If we are talking not about the steering wheel or stars, but about the fork legs, it is these anodizing properties that come to the fore. It serves to reduce friction between the legs and the guides inside the pants (bashings). A particularly important parameter is called starting - the start of leg movement from a state of rest. The more optimal it is, the more smoothly and without jerking your fork operates.

This is where a huge field opens up for healthy competition and various experiments with anodizing compositions and methods. And sometimes even within the same company. For example, Fox shock absorbers and forks have two versions, Performance and Factory, one of which has a simpler anodizing, and the second is more complex, called Kashima. Needless to say, prices and specifications vary markedly.

In general, the advantages of covering models of forks from different manufacturers can be found directly on their official websites.

And, of course, the aesthetic aspect has a certain significance. Anodized parts differ in appearance from painted ones.

For those who care about the appearance and color scheme of the bike, the market offers a huge range of multi-colored anodized parts, from stems and pedals to bonnets and tube caps.

This category also includes colorless coatings that produce interference effects when light is reflected. Having a reflective effect, this coating contributes to better visibility of the cyclist at night.

Features of caring for anodized coating

We'll talk about forks and shock absorbers. A scratch or abrasion on an anodized steering wheel most likely does not promise anything other than problems with aesthetics. But with moving legs everything is much more complicated and dramatic. Let's start with the fact that even a small scratch on the leg can cause huge problems, especially if it is located in the most mobile part of the leg. Therefore, ideally, you should try to avoid scratches and abrasions on your legs at all.

If evil fate nevertheless turns out to be inevitable, then try to carefully remove all the formed burrs with sandpaper. Otherwise, they will scratch the bashing and boots, and in retaliation they will develop the volume of the scratch, and everything will come to the point that a target of such a diameter will be formed that oil will begin to whistle out of it.

If the scratch or abrasion is really large-scale and unforgiving, bring it in for repair. There they will use powerful witchcraft, ranging from nail polish to restoring the coating. In this case, you are lucky, but this does not always happen. Perhaps everything is very bad and cannot be repaired at all. There is only one way out - donation. And in both directions.

Try to monitor the condition of the anthers and bushings, because, being clogged with sand, they have the unpleasant property of starting to peel off your feet. And also make sure that the fork does not work dry. It is fraught with the same problems.

Summary

If you're the proud owner of a sport mountain bike, it's likely equipped with a fork that has anodized legs. This is good, it is light, durable and responsive in operation. Keep an eye on it, change the oil on time, do not put the bike on your feet, check the bushings and, if possible, do regular maintenance, especially after using the bike in harsh conditions with a lot of dirt and dust. And then your bike will bring you a lot of positive emotions.

Source: https://bb30.ru/blogs/velo_choice/zachem-nuzhno-anodirovanie

Anodized aluminum

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.

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:

Protection from external influences;
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:

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).
A final rinse is carried out in a caustic solution.
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:

Not very high anti-corrosion resistance. When in contact with a chemically aggressive environment or metal, the anodized layer is exposed to oxygen.
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.

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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

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/

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.

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