Effect of alkalis and salts on metal anti-corrosion coatings and their degradation

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The action of alkaline solutions is primarily hydrolysis, as well as the formation of salts with the acidic groups in polymers, which makes the coating more hydrophilic and even causes it to swell and soften. The damage caused by salt solutions lies in the increased ion concentration; the penetration of ions leads to a decrease in the resistance of the coating. Some ions, such as chloride and sulfate ions, can also interfere with the function of corrosion-inhibiting pigments at the bottom of the paint film, thereby promoting corrosion of the metal beneath the coating. In terms of the stability in corrosive media, carbon-chain polymers are superior to hetero-chain polymers ； It is better when the hydrogen atoms on the carbon chain are replaced by fluorine or chlorine atoms (such as fluororesins) ； A higher saturation level and lower polarity are better than having more polar groups containing double bonds.