Can coating agents improve the corrosion resistance of metals?

Coating agents can improve the corrosion resistance of metals for the following reasons:

Forming a protective film

The coating agent forms a dense protective film on the metal surface through chemical reaction. This film can isolate the metal from the corrosive media such as air, moisture, acid and alkali, thereby preventing the metal from oxidation and corrosion. For example, the phosphating film formed on the surface of steel can effectively prevent the steel from contacting with water and oxygen, slowing down the speed of rusting.

Inhibit electrochemical corrosion: Metals are prone to electrochemical corrosion in electrolyte solutions. The film formed by the film agent can change the electrode potential on the metal surface, making the metal in a more stable state and reducing its corrosion tendency in the electrolyte solution. For example, after aluminum and its alloys are chemically oxidized, the oxide film formed can improve the corrosion resistance of aluminum products. This is because the oxide film changes the potential of the aluminum surface, making it less susceptible to corrosion in the air.

Enhance surface hardness

The film formed by some coating agents not only has good corrosion resistance, but also improves the hardness and wear resistance of the metal surface. This can reduce the damage to the metal surface caused by mechanical effects such as friction and collision, and avoid accelerated corrosion caused by surface damage. For example, in the hard chrome plating process, the chromium layer not only has excellent corrosion resistance, but also makes the metal surface more wear-resistant, thereby increasing the service life of metal products.