a) Ma Keng: Ma Keng is the result of organic pollution. A large pit usually indicates oil pollution. If the stirring is poor, the bubbles cannot be expelled, which will form pits. Wetting agents can be used to reduce its impact. We usually refer to small pitting as pinholes. Poor pre-treatment, metallic impurities, low boric acid content, and low plating temperature can all cause pinholes. Maintenance and process control of the plating solution are crucial, and anti pinhole agents should be used as process stabilizers to supplement.

　　b) Roughness and burrs: Roughness indicates that the solution is dirty, which can be corrected by sufficient filtration (high pH can easily form hydroxide precipitates and should be controlled). If the current density is too high, impurities are brought in by impure anode mud and added water, and in severe cases, roughness and burrs will be produced.

　　c) Low adhesion: If the copper coating is not fully oxidized, the coating will peel off and the adhesion between copper and nickel will be poor. If the current is interrupted, it will cause the nickel coating to peel off on its own at the point of interruption, and severe peeling may also occur when the temperature is too low.

　　d) Brittle coating and poor weldability: When the coating is bent or subjected to some degree of wear, it usually shows brittleness. This indicates the presence of organic or heavy metal contamination, excessive additives, entrained organic compounds, and electroplating corrosion inhibitors, which are the main sources of organic pollution and require treatment with activated carbon. Insufficient additives and high pH can also affect the brittleness of the coating.