Iron corrosion occurs when it interacts with atmospheric oxygen. To avoid this and extend the service life of the product several times, it is necessary to carry out a set of protective measures. Usually galvanized. This process consists in applying a layer of zinc to the surface of the product. This process can go through various methods.
Varieties of operation
To date, the progressive development of scientists allows you to use the following types:
- cold galvanizing of metal;
- hotter;
- diffusion;
- electrolytic;
- shoping;
- gas-dynamic.
We will talk about each method separately later.
Description of the types of galvanizing
Two types can be considered widespread - hot and electrolytic. In this case, the first method, also called galvanic, requires the installation of an entire line in production. But this method is ineffective against corrosion. However, it gives the product a beautiful and shiny appearance. So use electrolytic galvanizing only for decorative purposes.
Hot dip galvanizing is a very expensive undertaking. For its implementation, the part must be completely immersed in molten zinc. Such a process is carried out only on an industrial scale and requires a lot of energy and labor. The surface of the product is not glossy, but matte. But the layer is so strong that it can be compared in terms of corrosion resistance with stainless steel.
Hot and cold galvanizing is well established as a means of protecting metals. When zinc powder or steam is applied to the surface of an article using high temperature, this process is called a diffusion coating. If zinc in the molten state is applied with a gun, like staining, then this is a hoop.
The process of applying zinc using a supersonic flow is a gas-dynamic coating. This method has increased adhesion and is very advantageous in this regard in comparison with others.
All these methods can easily be deployed on an industrial scale in a special production, but at home these processes will be very difficult to use, and in some cases simply impossible.
In order for the metal structure to meet the stated requirements and terms of operation, it must be manufactured in accordance with the conditions of regulatory documentation. Such requirements are clearly spelled out in GOST.
Cold galvanizing is the most common and affordable way to protect iron from corrosion. He does not need special equipment and complex technological processes. Applying a zinc-containing compound is no more difficult than applying paint.
The content of the composition, which is used for cold
galvanizing of metal, is clearly regulated by GOST. It should have at least 94 percent zinc.
What is this element?
Zinc is a chemical element belonging to the group of metals. It has a silver-white color. In its pure form has a rather fragile structure. It reacts with atmospheric air, namely with its components: carbon dioxide and oxygen. Due to this reaction, oxide appears on the surface of the part, which has high bond strength and is not subject to dissolution.
The electrochemical potential of zinc is halved compared to iron. Therefore, the pair of compounds is an anode in the form of zinc and the cathode is iron. When exposed to atmospheric moisture, zinc reacts with it, and carbonate forms. It is he and his oxide that do not dissolve, but cover the product with a film.
The advantages of cold working
- The method of cold galvanizing has the main advantage - this is the absence of restrictions on the volume of the processed product.
- There is no need to dismantle the product and deliver it to the place of processing. Everything can be done stationary.
- The surface galvanized in this way does not interfere with welding. You can also weld.
- Cold processing of metal structures with zinc occurs at a comfortable temperature - from -20 to + 40 degrees.
- The coating effectively protects against corrosion, and itself is not subject to serious deformations, as it turns out to be very elastic.
- Cold galvanizing allows you to apply various coloring compounds to the surface.
- Work can be done independently, without the availability of special equipment and machinery.
- Cold galvanizing GOST 9.305-84 is clearly regulated by composition and properties.
- Low cost.
Do it yourself
Such a coating that protects the metal from corrosion can be carried out at home, while observing caution. In addition to the cold method, galvanic treatment can be carried out. But you need to keep in mind that such an electrolyte is an extremely toxic substance. It must be handled carefully and carefully, it is imperative to have personal protective equipment.
The construction market presents a wide selection of tools that allow cold galvanizing of metal structures at home. Sometimes the content of the main element in them varies in a wide range. Accordingly, the effectiveness will be the lower, the lower its percentage.
Such compositions may have other disadvantages:
- the need for more thorough preparation of the part;
- poor adhesion to metal, as a result of which microcracks form on the coating due to poor elasticity;
- some manufacturers use only a specific solvent, which complicates the work;
- for applying some, a special apparatus is needed;
- others are simply not provided for further painting.
"Galvanol"
Good characteristics and recommendations of consumers, such material as "Galvanol" possesses.
Its properties:
- It has a high content of pure zinc powder, which reaches 96%;
- quick drying, before applying the following layers you need to wait no more than half an hour;
- it is possible to apply a similar galvanizing cold by any known method: brush, roller, dipping or spray gun;
- suitable for further painting with paints and varnishes, as well as polymer coatings;
- it is possible to apply without preliminary cleaning of rust;
- does not lose its properties when applied at low temperatures (up to -35 degrees), as well as with moisture on the part;
- does not require a special solvent. Universal ones, such as solvent or xylene, are suitable.
Consumers conducting this galvanizing cold galvanizing reviews leave mostly positive. The metal is resistant to corrosion for several years.
How is it made
Processing Technology:
- Liquid zinc is well mixed, because it has a high density and delaminates. It is necessary to obtain a homogeneous liquid mass. How well prepared the material is to protect the product depends on how long this anti-corrosion layer lasts;
- clean the part mechanically;
- degrease the surface in any way possible;
- apply the next layer of the composition no later than half an hour later. Protection in two layers of zinc will last at least 10 years;
- The final layer, which will give the product a finished look, is better to apply, after waiting a day.
When cold galvanizing is performed, the technology must be followed. Only after that the result of homework will not be distinguished from the factory.
Galvanic
Any galvanizing requires great accuracy and accuracy, especially at home. The current source with this method can be a car battery or any charger with a capacity of up to 12 V.
Salt is suitable as an electrolyte. But it is better if it will be zinc. To make it you need:
- zinc sulfate - 200 g;
- magnesium or ammonium sulfate - 50 g;
- sodium acetate - 15 g;
- litere of water.
You can make salt by another method by placing zinc in a battery electrolyte and waiting for the reaction to complete, after which the acid will be converted to salt. Moreover, its concentration may be high. Then the salt is diluted with water.
Important! Electrolyte is poison, work with it must be done with extreme caution. The room must be well ventilated during work.
Dishes for processing should be glass or from special plastic. A zinc electrode is attached to it. With a small amount of detail, a simple business can is suitable. The part must be well cleaned and degreased. It should be lowered into the prepared solution for no longer than 10 seconds. Then pull out and rinse thoroughly with water. After this, you need to anodize the part. For this, a zinc electrode is made, connected to a power source. The formation of a zinc film occurs within 10-40 minutes.
The cost of compositions for cold galvanizing
The composition of the "Barrier Zinc" content of the active substance is 96%. The term of protection is from 10 to 50 years. It has high efficiency, as it has a consumption of only 1 kg per 4 m 2 . Cost - from 300 rubles per kilogram.
"Zinol" - zinc-containing paint with a 95% content of the active substance. Cost - from 340 rubles per kilogram.
Zinga is a Belgian-made composition that allows cold galvanizing, which has all the necessary properties to protect metal from corrosion. Cost - from 576 rubles per kilogram.
The "Galvanol" already mentioned by us is the most popular remedy among analogues. It has a 96% zinc content in the composition and all the necessary properties. Cost - from 390 rubles per kilogram.
"Zinotan" - contains only 85% zinc. Cost - from 380 rubles per kilogram.
Zinc-based protective compounds are available in a huge assortment. The price depends not only on the content of zinc, but also on the fame of the issuing brand. Another composition that allows cold galvanizing is Zinol.
How to choose the right
When buying the necessary funds, it is better to pay attention in advance to its composition and declared properties. Color shades do not differ in variety, mainly matte gray. Application rate is almost the same - no more than 300 g / m 2 .
Therefore, these criteria cannot be considered key when choosing, but what really matters is:
- life time;
- cost;
- drying time;
- zinc content;
- shelf life;
- application conditions.
Conclusion
So, we found out how cold galvanizing of metal structures is made. As you can see, this is a great way to protect the metal surface from the negative effects of corrosion, thereby increasing its life.