How do anodic and negative coatings protect the base metal?
What are anodic coatings and cathodic coatings? According to the electrochemical relationship between the coating metal and the base metal, the coatings can be divided into anodic coatings and cathodic coatings. Under normal conditions, the electrode potential of the coating metal is higher than that of the base metal. When the electrode potential is negative, it is called anodic coating, otherwise, it is called cathodic coating. What is the protective effect of anodic coating and cathodic coating on the base metal? The protection principle of anodic coating is based on the fact that the potential of the coating is negative compared to the base metal, and its electrolytic pressure is larger, and it becomes the anode in the corrosion battery, thereby delaying the delay. Corrosion of base metal. Even when the base metal is slightly exposed, the coating can still play a protective role. Therefore, the number of pores on the anode coating has little effect on the protective performance. In terms of thickness, the larger the thickness of the coating, the stronger the protective effect. The cathodic coating only has a purely mechanical isolation effect on the base metal, and has no electrochemical protection effect like the anodic coating, so it must have a protective effect when the porosity of the coating is very small. Otherwise, in the pores or damage of the coating, The base metal will act as the anode of the corrosion cell, accelerating the corrosion of the base metal. Generally, the porosity of the coating decreases with the increase of the thickness of the coating, so the greater the thickness, the stronger the protective performance of the cathode coating.
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