Material Dynamics - Advances in the research of water-based rust-resistant coatings

The most effective, simple and economical way to slow corrosion on steel surfaces is to paint them with rust-proof coatings. In order to obtain excellent anti-corrosion performance, the traditional process of rust on the substrate completely removed, and requires the substrate to reveal a metallic luster, the work is quite heavy, low production efficiency, high construction costs, and rust dust on the human body is extremely harmful. Therefore, it is necessary to develop a coating that can be directly constructed on a certain rust surface, while reducing the cost of coating, it can also simplify the painting process, reduce labor intensity, reduce the harm of rust dust to human body and environmental pollution
solvent-based rust-proof coating, paint contains a large number of volatile organic solvents and heavy metals, such as high toxicity, and flammable, explosive, serious environmental pollution. In order to overcome the shortcomings of solvent-based rust-resistant anti-corrosion coatings, water-based rust-proof coatings have been studied at home and abroad, water-based coatings in transportation, coating, application, cost has a great advantage, not only safe, but also good for the environment, save resources, so the development of water-based rust-resistant anti-rust coatings is currently the focus of research.the anti-rust principle of
stable water-based anti-rust coating is that the reaction group of the base resin itself is used, and the solid reaction between the active anti-rust pigment and the rust layer added to the coating should be reversed, the reaction in the coating to produce a stable polyic acid compound, so as to achieve the effect of stable rust, so that the rust layer becomes one of the coating fillers. At present, the active rust-proof pigments used in stable rust-proof coatings typically use chromate, phosphate, ferrate and so on. The hydrolyzing of the active pigment can produce acid ions, which can react with the lively rust acid in the rust layer, generate mates, play a stabilizing effect on rust, make rust inactive, and prevent steel from continuing to corrode. Different amount of anti-rust pigment addition, can be prepared for steel surface corrosion conditions are wide, the application of a wide range of water-based rust-proof coating.
. Transformed water-based rust-proof coating
conversion-type water-based rust-proof coating can also be called reaction-type rust-resistant paint, paint contains a chemical reaction of energy and rust conversion agent, the substance can make the corrosion product rust into a certain protective effect on the substrate of the compound or chelate, common phosphoric acid, potassium iron cyanide, hydrolytic acid and so on. Transformed water-based rust-proof coatings contain organic acids, inorganic acids and other conversion agents, and rust reaction is faster, therefore, the rust layer thickness can reach (40 to 100 m) of steel surface construction, suitable for uniform rust layer and no old coating and residual oxidation skin of the steel surface. The disadvantage of the coating is that it is difficult to accurately determine the relationship between rust layer thickness and uniformity and the amount of conversion fluid, such as insufficient conversion fluid, rust can not be completely converted;
. Permeable water-based rust-proof coating
permeable water-based rust-proof coating itself does not react with rust, but by selecting a strong permeable resin as the base resin of the coating, and with the help of permeable agents and polar solvents, the coating has good permeability in the rust layer, thus surrounding the loose rust and separating it from the substrate. Effectively will protect the substrate, corrosion products (rust) and the external corrosion medium isolation, so that rust inactive, while enhancing the rust layer, coating, steel plate adhesion between, thereby preventing the more positive bit of rust and the lower likely steel electrochemical reaction, resulting in new rust. The disadvantage of the coating is that the cost is high, the wide range of promotion is difficult, so the application is less.
. Functional water-based rust-proof coatings
functional water-based rust-proof coatings bring together the common characteristics of stable, transformational and permeable coatings, while improving the base resin, so that the base material becomes a characteristic that can react with water, neutral the residual moisture in the rust layer, to effectively remove moisture from the rust layer, enhance corrosion resistance. Some functional water-based rust-proof coatings have the function of oil coating, and still have strong anti-corrosion properties when the surface of the substation is incomplete. Mainly according to the oil molecules are basically alkane organic matter, the use of phase-soluble principle, so that oil molecules and coating substrates, additives, etc. emulsification reaction, so that oil molecules from the substrate stripped down, into the paint as a plasticizer exists.the choice of
resin
according to the performance and matching of the resin to choose, because aolic acid resin is only applicable to ordinary solvents (gasoline, ethanol, etc.) made paint matching, and phenolic resin release period is short, not easy to produce and apply. Therefore, at present, it is widely used in water-based rust-proof coating film-forming substances are mainly epoxy resin, polyurethane resin, acrylic resin and phenyl propylene emulsion.
. . . pigment selection
research shows that the steel surface rust is generally composed of two layers of rust, the outside is looser for fiber rust, the inner magnet rust continues to lose electrons to become the outer layer of fiber rust, so to prevent corrosion continues to occur, just to prevent the loss of electrons, or reduce the difference in the position of metal corrosion. The addition of active pigments to coatings improves the anti-corrosion properties of coatings. Commonly used anti-rust pigments are phosphate, ZnO, talcum powder, palladium sulfate, etc. , because phosphate on the base resin has a wide range of choices and more varieties, so phosphate rust-proof pigments are used the most, the best anti-rust effect. Mainly by using the strong reducing of these pigments, reduce the rusty maye, reduced to a relatively stable iron structure of steel substrate.
. The main role of the conversion agent
conversion agent is to react with rust, enhance the conversion rate of rust in the coating, so that the steel surface potential is positive rust into a network, inhibit rust further corrosion of the steel foundation, thereby improving corrosion resistance. The traditional use of red dan system, chromium-containing system as a converter paint due to more toxicity, for environmental considerations have not adapted to the development needs of today's society. At present, the commonly used conversion agents are mostly used daninate-phosphoric acid. Danning acid-phosphoric acid rust converter has the advantages of low toxicity and renewable danning acid. In the presence of phosphoric acid, deninic acid easily and steel surface and rust layer of Fe3 plus in the process of a new reaction, forming a stable ensetter. Daning acid 13 hydroxyphenol derivatives can be multi-point with iron, forming a mesh structure of the protective film, firmly adsorbed to the surface of steel. The effect of danning acid-phosphoric acid rust converter depends on the type of deninic acid, the concentration of phosphate, the corrosion of steel, the reaction time of rust and conversion agent, the influence of other additives and the method of use.
water-based rust-proof paint solvent for water, no organic solvents, will not cause pollution to the environment, can be in poor ventilation conditions under the circumstances of construction, without taking into account the risk of solvent volatility leading to explosion. For steel surfaces that can not be completely rusted can be applied directly without affecting the corrosion resistance of the coating, so water-based rust-resistant anti-rust coatings are widely used, but due to its comprehensive performance there are shortcomings, more in-depth research is needed. The development of more multi-functional water-based resins, so that the film material performance is more excellent, but also excellent rust conversion and stabilization function. Additives also need to develop more supporting new additives, so that water-based rust-proof coating performance to a higher level.