cathode current density

Any plating solution has a current density range for obtaining a good coating. The minimum current density for obtaining a good coating is called the lower limit of current density, and the maximum current density for obtaining a good coating is called the upper limit of current density. Generally speaking, when the cathodic current density is too low, the cathodic polarization effect is small, and the crystalline grains of the coating are relatively coarse. Low cathodic current density is rarely used in production. As the cathodic current density increases, the polarization effect of the cathode also increases (the increase in polarization value depends on various electroplating solutions), and the crystallization of the coating also becomes fine and tight; However, the current density on the cathode cannot be too high and cannot exceed the allowable upper limit value (different electroplating solutions have different upper limit values of cathode current density under different process conditions). After exceeding the allowable upper limit value, due to the serious lack of metal ions near the cathode, metal coatings with shapes like tree branches will be produced at the tip and protrusion of the cathode Alternatively, a loose coating in the shape of a sponge can be generated on the entire cathode surface. In production, it is common to encounter the phenomenon of "burning" at the sharp corners and edges of parts, and in severe cases, it can form dendritic crystals or sponge like coatings.