First, the role of anti-corrosion coating
1, shielding effect. The paint film prevents the corrosive medium from contacting the surface of the material and blocks the passage of the corroded battery to increase the resistance.
2, corrosion inhibition. Certain pigments, or their reaction products with film formers or moisture, can act to inhibit the substrate metal (including passivation).
3, cathodic protection. The film electrode potential is lower than the substrate metal. In an etching cell it is "sacrificial" as an anode so that the substrate metal (cathode) is protected.
Second, the main factors affecting anti-corrosion coatings
1. Effect of Coating Filming Substances
The film-forming substance of the anti-corrosion coating has chemical stability in the corrosive medium, and its standard is related to the composition and chemical structure of the film-forming substance. The main point is to see if it is easy to react with corrosive media under dry film conditions or decompose into small molecules in the media.
The shielding effect of anti-corrosion coating is very important from the viewpoint of anti-electrochemical corrosion and pure isolation. The shielding of the film depends on the structural pores and coating pinholes of the film forming material.
Water, oxygen, and ions penetrate the paint film at different rates. Water penetrates much faster than ions. Oxygen is relatively complicated to pass through and has a large relationship with temperature. Water and oxygen penetrate the paint film to form corrosion electricity on the metal surface. Ions penetrate the paint film less, regardless of their direct effect on the substrate metal, but will increase the conductivity of the paint film.
When the molecules in the film-forming structure have more functional groups, the structure of the film has fewer pores and can react with each other during the film formation process to form a network-like three-dimensional structure with high crosslink density, thereby enhancing the corrosion resistance of the coating.
The physical and mechanical properties of the paint film largely affect the anti-corrosion effect of the anti-corrosion paint. They are related to the molecular weight of the film forming material, chain segments, side genes, and the like.
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