What are the common problems with hard chrome plating?
2 Answers
Common problems with hard chrome plating are as follows: Peeling of the plating layer: Improper current density of the mold chrome plating anode affects the bonding strength of the plating layer. Excessive current density can cause the hard chrome plating layer to peel easily, so it is essential to control the cathode current density within the specified process range. A high content of SiF6 in the plating solution can also make the black chrome plating layer prone to peeling. Poor wear resistance of the hard chrome plating layer: Comparative production practices show that improper content of main components affects the wear resistance of the black chrome plating layer. If the CrO3 content in the plating solution is below 250g/L, the wear resistance of the plating layer is poor. When the H3BO3 content is below 20g/L, the plating layer crystallizes coarsely, and both hardness and wear resistance decrease. During the plating process, improper control of the anode-to-cathode area ratio can also reduce the wear resistance of the plating layer. Typically, an anode-to-cathode area ratio ranging from 1:5 to 1:10 is more favorable.
The most common issue with hard chrome plating is peeling and flaking of the coating, which we in mechanical maintenance see all the time. Last time I was repairing a hydraulic rod, I encountered this—the coating lifted like a snake shedding its skin. This is usually because the base metal wasn’t properly cleaned, with oil or oxide scale remaining, so the chrome layer couldn’t adhere properly. Another annoying problem is pitting—the surface becomes uneven, like the surface of the moon, mostly due to impurity particles floating in the plating solution. In my twenty years in this field, the most dreaded issue is brittle plating, especially with thick coatings. A light tap with a hammer can cause spiderweb cracks—often due to poor control of plating solution temperature or current density. My advice is to inspect the base metal’s polish with a magnifying glass before each plating run—it saves a lot of hassle compared to rework later.
