How anodic and cathodic coatings protect the base metal
[Abstract]：
How anodic and cathodic coatings protect the base metal
What are anodic and cathodic coatings? According to the galvanic relationship between the plating metal and the base metal, the plating can be divided into anodic plating and cathodic plating. Under normal conditions, the electrode potential of the plating metal is higher than that of the base metal. When the electrode potential is negative, it is called anode plating, otherwise it is called cathode plating. What is the protective effect of anode coating and cathode coating on the base metal? The protection principle of the anode coating is based on the fact that the potential of the coating is negative compared to the base metal, and its electrolysis pressure is large, which will corrode the anode in the battery, thereby delaying Corrosion of base metal. Even when the base metal is slightly exposed, the coating can still provide protection. Therefore, the amount of pores on the anode coating has little effect on the protection performance. As for the thickness, the larger the thickness of the coating, the stronger the protection. Cathodic coatings only provide pure mechanical isolation for the base metal, and do not have electrochemical protection like anode coatings, so they must be protected only when the porosity of the coatings is small. Otherwise, the pores or breakage of the coatings, The base metal will serve as the anode of the corroded battery, accelerating the corrosion of the base metal. Generally, the porosity of the coating decreases as the thickness of the coating increases, so the larger the thickness, the stronger the protective performance of the cathode coating.
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