How to protect metal from corrosion
The development of the steel industry is inextricably linked with the search for ways and means to prevent the destruction of metal products. Corrosion protection, development of new techniques is a continuous process in the technological chain of production of metal, metal products. Iron products come into disrepair under the influence of various physical and chemical external environmental factors. These consequences we see in the form of hydrated iron residues, i.e. rust.
Types of corrosion
Methods for protecting metals from corrosion are selected depending on the conditions in which the products are used. Therefore, there are distinguished:
- Corrosion associated with atmospheric phenomena. It is a destructive process of oxygen or hydrogen depolarization of metal. Which leads to the destruction of the crystal molecular lattice under the influence of a humid air environment and other aggressive factors and impurities (temperature, the presence of chemical impurities, etc.).
- Corrosion in water, primarily sea water. It is faster because it contains salts and microorganisms.
- Destruction processes which occur in soil. Soil corrosion is quite a complex form of metal damage. Much depends on the composition of the soil, humidity, heating and other factors. In addition, products, for example pipelines, are buried deep in the ground, which makes it difficult to diagnose. And corrosion often affects individual parts pittingly or in the form of ulcerated veins.
Types of corrosion protection are chosen individually, depending on the environment in which the protected metal product will be – link.
Characteristic types of rust damage
The way steel and alloys are protected depends not only on the type of corrosion, but also on the type of damage:
- Rust covers the surface of the product as a continuous layer or in separate areas.
- Appears in the form of spots and penetrates point by point into the depth of the part.
- Destroys the metal molecular lattice in the form of a deep crack.
- In a steel product composed of alloys, one of the metals fractures.
- Deeper extensive rusting, when not only the surface is gradually broken, but also penetrates into the deep layers of the structure.
The types of lesions can be combined. Sometimes they are difficult to identify immediately, especially when pitting of steel occurs. Methods of corrosion protection include special diagnostics to determine the extent of the damage.
A distinction is made between chemical corrosion without the occurrence of electric currents. When in contact with petroleum products, alcohol solutions and other aggressive ingredients, a chemical reaction occurs, accompanied by gas emissions and high temperature.
Electrochemical corrosion is when a metal surface comes into contact with an electrolyte, particularly water from the environment. In this case, metal diffusion occurs. Under the influence of the electrolyte, an electric current is generated, and the electrons of the metals that make up the alloy are replaced and moved. The structure breaks down and rust is formed.
Steel smelting and corrosion protection are two sides of the same coin. Corrosion causes enormous damage to industrial and commercial buildings. In the case of large-scale technical structures such as bridges, power transmission towers, barrier structures, it can also provoke man-made disasters.
Metal corrosion and how to protect against it
How to protect metal? There are many ways to protect against metal corrosion. To protect metal from rust, industrial methods are used. Various silicone enamels, varnishes, paints, polymer materials are used in the home.
The protection of iron from corrosion can be divided into several main areas. Methods of corrosion protection:
- Passivation. Other metals (chromium, nickel, molybdenum, niobium, and others) are added when steel is produced. They are characterized by improved quality characteristics, refractoriness, resistance to aggressive environments, etc. As a result, an oxide film is formed. Such steels are called alloyed steels.
- Coating the surface with other metals. Different methods of protecting metals from corrosion are used: galvanizing, immersion in a molten composition, application to the surface with special equipment. A metal protective film is formed as a result. Chromium, nickel, cobalt, aluminum and others are most often used for this purpose. Alloys are also used (bronze and brass).
- The use of metal anodes, protectors, often made of magnesium alloys, zinc or aluminum. As a result of contact with the electrolyte (water), an electrochemical reaction begins. The protector breaks down and forms a protective film on the steel surface. This technique has proven well for underwater parts of ships and drilling rigs at sea.
- Acid etch inhibitors. The use of substances that reduce environmental exposure to the metal. They are used for preservation, storage of products. And also in the oil refining industry.
- Corrosion and metal protection, bimetals (cladding). It is the coating of steel with a layer of another metal or composite composition. Under the influence of pressure and high temperatures, diffusion and bonding of surfaces takes place. For example, the well-known bimetal heating radiators.
Corrosion of metal and methods of protection against it, used in industrial production, is quite diverse, it is chemical protection, coating with glass enamel, enameled products. Steel is hardened at high, over 1000 degrees Celsius, temperatures.
Protecting metals against corrosion in the home is primarily a chemistry for the production of paint and varnish materials. Protective properties of compositions are achieved by combining different components: silicone resins, polymers, inhibitors, metal powder and chips.
To protect the surface from rust, it is necessary to use a special primer or rust converter before painting, especially for older structures.
What kinds of converters there are:
- Priming agents – provide adhesion, adhesion to the metal, level the surface before painting. Most of them contain inhibitors that significantly slow down the corrosion process. Pre-applying a primer coat saves paint considerably.
- Chemical compounds – turn iron oxide into other compounds. They are not susceptible to rusting. They are called stabilizers.
- Compounds that convert rust to salts.
- Resins and oils that bind and seal rust, thus neutralizing it.
These products contain components that slow down rust formation as much as possible. Converters are included in the product line of manufacturers who produce metal paints. They come in different consistencies.
It is better to choose a primer and paint from one company so that they match the chemical composition. Beforehand, it is necessary to decide what methods you will choose to apply the composition.
Protecting metal in the home
Corrosion, ways to protect against it in domestic conditions require a certain sequence:
- Before applying a primer or rust converter, the surface is thoroughly cleaned of dirt, oil stains, and rust. Use metal brushes or special attachments for a grinder.
- Then apply a priming coat, allow to soak and dry.
- Then the product is painted in two layers. Let the first coat dry beforehand. When working it is necessary to use protective equipment (gloves, goggles, respirator).
Protecting metals against corrosion is a complex process. It begins at the stage of melting steel. It is difficult to list all the methods to combat rust, as they are constantly being improved, not only in industry, but also for domestic use. Manufacturers of paint and varnish products are constantly improving formulations, increasing their corrosion properties. All this significantly prolongs the life of steel structures and steel products.