Man conquered nature when he learned to process metals. Products from iron alloys with various components have transformed the world beyond recognition. The main disadvantage of metal products has always been the ability to oxidize, especially in the presence of water. Rust greatly shortens the life of any metal. For many millennia, metal processing technologies have evolved. Rust protection techniques have been improved.
In the 21st century, the widespread use of metal has greatly supplanted polymer and composite materials. But even so, the rust problem is not a thing of the past.
What is rust
Iron, used as the main component of many metal alloys, is highly reactive when combined with the carbon present and s alts dissolved in water. The resulting iron oxides cover the metal with a thin layer. Subsequently, they react with oxygen and water, the metal is completely destroyed, rust is formed.
Also,Rust refers to hydroxides formed under the influence of carbon dioxide or sulfur dioxide. The latter components are almost always present in water. Unlike oxides, they do not cover the main body of the metal with a dense layer, but form a thin film that peels off from the main mass. This opens the way for external influence of aggressive environments.
As long as there is iron surrounded by oxygen, water, carbon dioxide and sulfur dioxide, the process cannot be stopped.
Why paint is needed
Paints for metal play a significant role in corrosion protection. The chemical composition is selected in such a way that they form a stable film on the surface. Due to adhesion, the substance penetrates into the structure of the material and practically becomes one with it. The outer layer forms a thin film that is not exposed to aggressive environments. Thus, the paint plays not only the role of a decorative coating, but also serves as a protective mechanism against metal corrosion.
From what has been said, it is clear that adhesion and resistance to external influences are important indicators of the quality of paint for metal. Among which stands out:
- Fire safety.
- Chemical resistance.
- No UV exposure.
- The number of freeze-thaw cycles without losing their properties.
- Shock resistance including vibration resistance.
Depending on the chemical composition, all paints can be divided into several groups.
Epoxy enamels
Epoxy resins are often used as a base to create heat-resistant paints for metal. The property of resin to create a durable film on the surface is highly valued. Such a base is practically not subject to chemical influences, has high fire safety rates. Due to various additives, a certain viscosity is achieved, which makes the painted surface resistant to vibration. It is no coincidence that such compositions are widely used in the automotive industry.
Epostat primer-enamel can be considered as a base material. The main advantage of this enamel is a high drying rate and resistance to temperature extremes. It is almost unaffected by oily products, s alt and fresh water.
The main disadvantages of epoxy based paints for metal are their high cost and difficulty in application.
Oil paints
A relatively cheap option for rust protection are paints for metal based on drying oil. The main advantage of such a coating is a high degree of protection of the metal from the effects of the external environment. Water cannot penetrate through such a layer. In addition, manufacturers produce a wide range of colors of such coatings. This property makes them popular as exterior metal paints.
As an example, we can cite the high-quality trademark "Lakra" with a product line that meets all the requirements of painting.
Material propertyform an impenetrable film plays a bad joke with him. Simultaneously with protection from aggressive environments, gas exchange is blocked by the mass of the structure. This results in flaking and blistering, shortening the life of the coating and requiring regular repainting.
Alkyd coatings
Alkyd-based coatings are widely used. Usually the solvent is white alcohol. The high volatility of this substance accelerates the drying process of the surface. A mixture of solvent, alkyd, pigments with various additives and neutral gas made it possible to create a new painting tool - paint for metal in cans.
The wide variety of color shades and the ease of use of these aerosols have made them attractive for many applications. It turns out a uniform coating of the surface and deep filling of all its pores.
Surfaces coated in this way do not lose their qualities for a very long time. The price remains affordable for the average consumer. One of the leaders in this market is the Hamerite trademark.
Acrylic powders
The development of petrochemistry made it possible to develop and produce materials with previously unknown properties. Thus, polymer-based paints for metal were born. Due to the fact that ordinary water serves as a solvent, such materials have been widely used. The process of coloring has been greatly simplified, and the quality of work has increased.
Polymer powders enabled the creation of new processing technologiessurfaces. Under the influence of high temperature, powder paint for metal lays down, forming a perfectly flat surface, very reminiscent of enamel. The polymerization process makes it possible to create highly decorative surfaces with very good protection of the bulk of the metal. The consumption of the coloring composition remains minimal per unit area. The main disadvantage of such technologies is the availability of specialized equipment.
Hammer surfaces
Hammer paints for metal are classified not by the chemical composition of the substance, but by the presence of special additives. The composition itself can have any filler - epoxy, acrylic or alkyd. More importantly, what additives are used to give the hammer effect. The most commonly used are fine glass fractions and aluminum powder. The surface covered with such a composition has very interesting decorative qualities, reminiscent of hand chasing with a hammer. The defects of the painted surface are lost.
An example is the Dali trademark. Such enamels fit well on a rusty surface and ensure the safety of the metal for up to 8 years. Often fire retardants are created on their basis. An interesting side effect is that surfaces become dirt-repellent.
Primer-enamel
As already noted, one of the main characteristics of a quality surface treatment is adhesion. When it comes to finishing a new surface, almost all paints have good adhesive properties. Another thing is coloring.old metal or objects operated in difficult conditions.
Under these conditions, it is customary to use primers for surface pretreatment. Such enamels have high adhesion. A top coat with better characteristics in terms of resistance to external influences fits well on a pre-prepared area.
The main qualities of primer enamels include:
- Formation of a film that prevents the penetration of water and air.
- Slowing down the corrosion process, which is achieved through additives that slow down chemical processes.
- Orthophosphoric acid, which is part of enamels, reacts with metal and rust. Iron phosphate is formed, which prevents further corrosion from developing.
- High adhesion allows the composition to penetrate even into the galvanized layer.
- Due to the inclusion of metal microparticles on the surface, a protector is formed.
- It is useful to apply such primers at high humidity.
The overview does not allow for a comparative analysis of various types of metal surface treatment. The main purpose of this article is to give an idea of the variety of protective paints for metal.
