The hard chrome layer plated by a factory is very rough, and the bonding force is not satisfactory. It was originally estimated that the pretreatment was not effective. Later, it was found on site that the operator hung the workpiece in the tank and immediately distributed current plating, and the workpiece was not pretreated.
In fact, the temperature requirement of the solution in the hard chromium plating process is very strict, and the range of temperature change is within ±2°C, otherwise the quality of the coating may be affected. If the preheating method is not adopted, the current is distributed immediately after the plated parts enter the tank, then at this time, it is possible that the surface temperature of the plated parts is too low (deviating from the process requirements) at the time of initial plating, resulting in a black rough deposit layer. The chromium layer that continues to thicken on the surface of the rough deposit layer will appear rougher, and the bonding force of the coating will also be affected. It can be seen that the preheating of the plated parts before hard chrome plating is very important.
Steel parts can be preheated directly in the chrome bath, and copper and copper alloy parts can be preheated in the hot Water Bath. In order to ensure the preheating effect of the plated parts, the preheating time should be determined according to the wall thickness of the plated parts during operation. The preheating time is slightly longer for thicker walls, and shorter for thinner walls. Generally, the control is 2~5min. can meet their respective requirements. For thin-walled parts that need reverse plating treatment, no preheating treatment is required, because the temperature of the plated parts itself can reach equilibrium with the temperature of the solution within the reverse plating time.
