How Anode Coating and Cathode Coating protect the base metal
What are Anode Coating and Cathode Coating? According to the electrochemical relationship between the plating metal and the base metal, the plating can be divided into Anode Coating and Cathode Coating. Under general conditions, the electrode potential of the plating metal is higher than the electrode potential of the base metal. When it is negative, it is called Anode Coating, otherwise, it is called Cathode Coating.
What is the protective effect of Anode Coating and Cathode Coating on the base metal? The protection principle of Anode Coating is based on that the potential of the coating is negative than that of the base metal, and its electrolytic pressure is larger, and it becomes the anode in the corrosion battery, thus delaying Corrosion of the 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 greater the thickness of the coating, the stronger the protective performance.
Cathode Coating only has a purely mechanical isolation effect on the base metal. It does not have the electrochemical protection effect like Anode Coating. Therefore, it must have a protective effect when the porosity of the coating is small. Otherwise, the pores or damage of the coating will cause the substrate. The metal will act as the anode of the corrosion battery, accelerating the corrosion of the base metal. Generally, the porosity of the coating decreases as the thickness of the coating increases, so the greater the thickness, the stronger the protective performance of the Cathode Coating.