The difference between anode coating and cathode coating

Metal products will undergo varying degrees of corrosion during use. The corrosion of steel parts is called rusting. All coatings can have a certain protective effect on the base metal, preventing it from corrosion, but the protective principle of different coatings on the base metal is different. According to the nature of the protective effect or the electrochemical relationship between the coating and the base metal, the coating can be divided into cathodic coating and anodic coating.
From a chemical perspective, the degree of activity of metals varies, and their activity is determined by the ability to replace hydrogen ions or other metal ions from the acid. This order of activity is the electrochemical order of the metal and an important basis for determining the polarity of the coating.
(1) Anodic coating
The activity of the coated metal is greater than that of the base metal. Under operating conditions, when the coating encounters corrosive media, it first corrodes to protect the base metal from corrosion, which has the characteristic of sacrificing the coating to protect the base metal. This coating is called an anode coating, such as zinc coating on steel.
(2) Cathode coating
The activity of the base metal is greater than that of the metal coating. Under usage conditions, only when the coating is completely wrapped around the base metal can it protect the base metal. If the coating is incomplete, porous, or damaged. When corrosion occurs, the base metal will be damaged due to corrosion, and the coating will not corrode, which will accelerate the corrosion rate of the base metal. This type of coating is a cathodic coating, such as copper coating, nickel coating, etc. on steel.
Due to the fact that cathodic coating only has a protective effect on the base metal when it is complete and has a certain thickness, from a protective perspective, anodic coating should be used as much as possible. If cathodic plating is to be used, it is required that the thickness and porosity of the plating layer meet the needs of the user.