Since people learned how to make metal, humanity has faced an acute question of ensuring the protection of the products obtained from destruction by corrosion. Rust is the main enemy of any metal surface to this day. The long-term improvement of methods and means designed to prevent corrosion, undoubtedly, allowed to achieve incredible results in the fight against natural chemical processes. Nevertheless, it is impossible to guarantee absolute corrosion resistance.
Is it possible to process the metal yourself at home?
Today, among the available methods of protecting iron materials from the influence of destructive factors, phosphating is worth noting. After carrying out the corresponding chemical reaction, the metal acquires increased wear resistance, which can significantly extend the period of its direct operation.
The best protection for iron from rust and rot is to coat its surface with a thin, barely noticeable film. At home, phosphating a metal seems to be a daunting task, relating to the impossible. Indeed, it is only in industrial shops that there is the necessary equipment, the required reagents. In fact, subject to a set of rules and conditions, any person who does not have professional technical education will be able to achieve the desired result.
Reagents needed for phosphating
An additional advantage of home phosphating is its versatility: a strong protective film is formed on the surfaces of almost any alloy, with the exception of high alloy steel.
In addition, the surface layer adheres perfectly to the base of the iron billet. As materials for metal phosphating use:
- manganese;
- zinc;
- iron phosphates.
Benefits of Iron Phosphate Treatment
Modern technologies for applying phosphoric acid chemical composition allow coating metal surfaces with a minimum thickness of not more than 5 micrometers. This method of processing iron prevents its destruction and provides protection from external influences, guaranteeing continued use of the metal product in any conditions, including:
- with excessive moisture;
- under the influence of aggressive chemical solvents;
- in contact with engine oils;
- at high electrical voltage;
- as a basis under a paint and varnish covering.
Phosphating the metal for painting will provide reliable protection to the material, but if it enters an acidic or alkaline environment, the product will still remain vulnerable. Moreover, when painting any iron surface, paint and varnish materials penetrate much deeper into the layers of a protective film with a high level of porosity. Improved adhesion of the surface of the alloys is another positive point, which allows one to say yes to phosphating before painting the metal.
Technology and methods of industrial phosphating
Before starting to apply the film layer, it is important to understand the composition of the medium in which the iron will be placed. The technology of phosphating the metal, followed by coloring with a paint and varnish substance is not suitable for home use. With the help of the drug "Majef", with the solution of which huge containers are filled at the enterprise, iron is coated with the thinnest, but very strong and practical layer.
A
metal product completely placed in a phosphating
bath is heated to extreme temperatures and boiled for half an hour. After this, the iron is removed, the film is allowed to completely harden, harden, at the end of the process, the surface is galvanized using abrasive or sandblasting machines.
Using the above method can be called justified only in the case of processing large structures. Such metal phosphating services provided in industrial metal rolling workshops will cost the customer a decent amount.
How to process metal at home: “cold” electroplating
For the galvanization of small products, it is more expedient to resort to elementary technology. We are talking about phosphating a metal with phosphoric acid, the preparation of which is available even at home. For a successful reaction, the correct concentration of chemical elements should be adhered to. The following are the components of the solution in the ratio of the amount of substance (in grams) per 1 liter of water:
- phosphoric acid - not more than 40;
- zinc nitrate - about 200;
- zinc oxide - 15;
- sodium sulfate - 8.
The procedure does not take much time - it takes about half an hour to prepare a solution and a direct chemical reaction. One of the main requirements that should be followed during the processing of iron is the correct concentration of the solution and its temperature (not less than +18 ° C and not more than +25 ° C).
This method allows to obtain cold phosphating of the metal at home, however, its quality is significantly inferior to the processing of iron products using the drug "Majef" - the maximum thickness of the obtained film, as a rule, does not exceed 5 microns.
Electrochemical phosphating of iron parts
Most of the technologies for processing metal products, which did not deserve popularity in the production, are successfully used by amateurs. Such is the electrochemical treatment of iron, which implies coating the surface with a reliable film due to the electrolyte reaction and current. The basis of the principle of action of this method is the use of phosphoric acid or the drug Majef.
An electrode is mounted on the iron billet to be phosphated. The structure is lowered into the bathroom with a solution prepared in advance, and zinc rods are used as the anode - they also need to be supplied with electricity. To qualitatively process metal, it is not at all necessary to resort to the use of a high-voltage network, 25 V of alternating or direct electric current is sufficient.
"Majef" - the best composition for the primer of metal before painting
The phosphating procedure does not last long - on average, up to half an hour. This technique is ideal for processing straight-line, medium-sized products. For objects with a more complex geometric design, a different method of phosphating iron should be chosen in order to avoid an uneven distribution of the galvanizing film.
Used in production and at home, "Majef" is a high-quality soil composition that has all the certificates and complies with GOST. Phosphating metal in an automobile body is one of the most common reasons for using a substance. In order to protect the car from rust, Mazhef is applied even in places where, as you know, the paint will not last long (for example, on the bottom of the car).
To start processing metal, dirt, dust, bitumen particles are removed from the surface and thoroughly degreased. The working mixture can be prepared independently, but it will significantly save time and will evenly distribute the composition of the aerosol release form. At the same time, some reagents are applied to the processed iron with a brush. But this distribution method is not suitable in the absence of experience in priming surfaces - it is extremely important to monitor the uniformity of the application of the phosphate composition.
Recommendations for the use of phosphate formulations
When processing small metal parts with "Majef", a hot method of layering a protective film also becomes possible. An alternative to the acquired composition can be considered a mixture of zinc nitrate and phosphoric acid.
During the preparation of the mass, one should not forget for a second about caution and basic safety precautions:
- It is advisable to wear special safety glasses.
- To prevent poisoning by vapors, work outdoors or in a ventilated area.
- At the end of the procedure, you should thoroughly wash your hands so that particles of chemicals do not get on the mucous membranes of the eyes and mouth.
Finishing after phosphating parts
As a rule, phosphating a metal at home is not the final step in processing a product. Since the porosity of the structure of the galvanic protective film can affect its further functionality and operational properties, the metal surface is passivated. As solutions that ensure smoothness and evenness of the coating, use potassium dichromate or sodium dichromate.
In the process of finishing metal, it is extremely important not to miss the temperature indicators: objects with phosphate films are immersed in 80-degree solutions and can withstand them for at least 20 minutes. After passivation, the products are treated with machine oil, after which a solution of gasoline and organosilicon liquid is used in a ratio of 1:10.
How to check the quality of the protective film on metal?
An indicator that the obtained coating corresponds to the declared characteristics is its fine-crystalline structure and the minimum number of pores. The specific gravity of the applied layer is also taken into account in the production: the film weight should not exceed three grams per 1 sq. Km. meter. Normal phosphating (metal processing occurs at boiling points) allows you to get a strong coating, the thickness of which can reach 7 microns, and with a cold type of exposure, the galvanizing layer leaves a smaller thickness, which means it has a lower quality.
A few tips on phosphating: what you need to know?
For successful phosphating of the metal outside the production halls, it is important to pay attention to the following points:
- The easiest way to prepare a phosphating paste, with which you can process vertical sections, is as follows: you need to mix "Majef" or a home-made solution of phosphoric acid and zinc nitrate with a neutral filler - talc, powder, kaolin. The main thing is to observe the proportion (3 parts of the solution for 2 friable substances).
- Degreasing components can be added to phosphate solutions - this will save strength at the stage of preparation for metal phosphating. To do this, add 1 g of water to 45 g of sodium nitrate and sodium monophosphate, as well as half a tablespoon of detergent. The residence time of the part in the phosphating bath should be doubled.
- To remove rust from the metal surface, complex polyphosphates must be added to phosphoric acid. A special wetting agent will help increase the efficiency of the prepared solution - it will clean the surface of the iron.
- Phosphating Accelerator - A substance added to a surface treatment composition. With it, the whole process takes a minimum of time.
Phosphate treatment of iron structures from any alloy
Given that the simultaneous conduct of several processes of metal phosphating is a significant advantage not only in industry but also in everyday life, this industry may become a potential direction for improving existing galvanic technologies. In addition to the financial savings that are obvious with home phosphating, this iron treatment has a number of other advantages. For example, phosphate compounds are capable of protecting not only black but also non-ferrous alloys (copper, cadmium, aluminum, etc.) from destruction.
To protect the metal from rust caused by external factors, climatic conditions, it is processed immediately after purchase. If the processed iron products are placed in a room with excessive humidity, a bluish coating may form on their surface - it does not pose any danger to the metal itself, and in practice it often acquires decorative significance.