Types and research progress of coatings in the field of metal anticorrosion

Corrosion of metals is the phenomenon that metals are destroyed by the chemical or electrochemical action of environmental medium The corrosion of metals has spread in all fields of national economy, which has brought huge losses to the national economy In the developed countries, the direct economic loss caused by corrosion accounts for 1% ~ 4% of the total national economic output value, the steel corroded and rusted accounts for about 20% of the output every year, and about 30% of the equipment is scrapped due to corrosion In China, the economic loss caused by metal corrosion is more than 30 billion yuan per year, accounting for 4% of GDP For a long time, people have been using a variety of technologies to protect metals from corrosion Among them, one of the most effective and commonly used methods to prevent corrosion of metal equipment is to apply anti-corrosion coating on the metal surface to isolate the corrosive medium and metal matrix As other coatings, the formulation of anticorrosive coating mainly includes base material (resin), pigment, filler and solvent The base resin is the film-forming material and the main component of the coating Its molecular structure determines the main performance of the coating The pigments and fillers are used to assist in the isolation of corrosion factors According to the mechanism of action, they can be divided into antirust pigments and sheet fillers The solvents are divided into organic solvents or water, which are used to dissolve the base resin and facilitate the film-forming In this paper, the latest research progress of common metal anticorrosive coatings is reviewed Epoxy resin coating epoxy resin is a thermosetting resin containing two or more epoxy groups per molecule on average Epoxy resin is widely used because of its easy processing, excellent curing properties and so on It can be made into anticorrosive coating by epoxy structural modification, epoxy alloying, filling inorganic filler, expansion monomer modification and other high-performance Epoxy resin coating has excellent physical and mechanical properties, the most outstanding is its strong adhesion to metal; its chemical resistance and oil resistance are also very good, especially the alkali resistance is very good The main components of epoxy resin coating are epoxy resin and its curing agent, and the auxiliary components are pigments, fillers, etc Stainless steel powder is a kind of metal pigment developed in recent years Because of its non activity, especially its excellent protection in high temperature and strong corrosion environment, it can be used as a main pigment, as well as a part of composite pigment, and as a protective coating with adhesive M Selvaraj found that the optimal combination of stainless steel pigment and epoxy resin can be realized by polarization method, and the powder epoxy coating can make up for the poor wear resistance of epoxy resin surface, so it can be directly used in the open air environment The coating is a two-component coating One part is to dissolve 70% of the epoxy resin in methyl isobutyl ketone, xylene, butyl synthetic rubber and other fiber dissolving agents; the other part is to dissolve 70% of polyamide in xylene, and the two can be mixed when used The results of mechanical, accelerated life and electrochemical tests show that the coating has good mechanical properties and long-term metal morphology stability in NaCl solution In order to improve the heat resistance of epoxy resin coating, people use the heat resistance of silicone to mix a small amount of silicone resin with epoxy resin to make a new heat-resistant and anticorrosive coating This is because the existence of - Si - O - Si - in silicone makes the coating have good thermal stability, while - Si - C - ensures the solid composition of the coating Firstly, epoxy resin and methyl isobutyl ketone are mixed to form a solvent, then silicone resin is added to the solvent, then xylene is used for dilution, and polyamide is added as curing agent Through the observation of spectroscope and electrochemical microscope, it can be found that the thermal stability of the coating has been significantly improved, and it has good resistance to toluene, trichlorotoluene and other solvents In addition, M dhanalakshmi et al Studied the epoxy resin coating and found that it had poor corrosion resistance in humid environment Ketimine was used instead of polyamide and polyamide The amine produced by hydrolysis of ketimine could react with epoxy resin, so as to achieve the purpose of water resistance and corrosion protection If epoxy resin is blended with chlorinated rubber and silicone resin to form polymer polymer type coating, the protection function of ordinary multilayer film can be realized by using the barrier of rubber to water vapor and the high temperature resistance of silicone