Causes and Treatment Methods of Local Blistering in the Plating Layer of Roll Plating Copper Nickel Workpieces

Causes and Treatment Methods of Local Blistering in the Plating Layer of Roll Plating Copper Nickel Workpieces

Possible cause: Low free NaCN

Reason analysis: The factory uses room temperature barrel plating cyanide copper plating, and the appearance of the copper coating is normal. After barrel plating nickel, the appearance of the nickel layer is also normal. After baking at around 100 ℃, the above phenomenon occurs.

If the workpiece coated with copper on the normal nickel plating is placed in the nickel bath where the "fault" occurs for electroplating, and baked at the same temperature, the test results show no bubbles, indicating that the nickel plating solution is normal. So the fault may have occurred in the copper bath. In order to further verify whether the fault occurred in the copper bath, the strictly pre-treated workpiece was placed in the "faulty" copper bath for electroplating, and then baked at the same temperature. The test results showed that the coating was foaming. It can be confirmed that the fault occurred in the copper tank.

The workpiece is bent to fracture and the coating is not peeling, indicating that the pre-treatment is normal. Peel off the blistering coating and find that the substrate is clean, which further indicates that there is no problem with the pre-treatment before electroplating.

Cyanide coatings generally have good adhesion and no brittleness. The main reasons for local blistering of the coating are insufficient free cyanide content or excessive impurities in the plating solution. After laboratory analysis, the content of cuprous cyanide is 14g/L, while the free content is only 4g/L. From the analysis results, it can be seen that the content of free sodium cyanide is low, the activation effect of the working surface is not strong, and it is easy to produce coating bubbles.

Treatment method: After adsorbing and treating the plating solution with 3-5 g/L activated carbon, analyze and adjust the composition of the plating solution to specifications. After electrolysis at low current for 4 hours, try plating.

It must be pointed out that the content of cuprous cyanide in the plating solution is also low. The content of cuprous cyanide in barrel plating should be above 25g/L at room temperature. If the content of cuprous cyanide is adjusted at the same time, the content of free sodium cyanide should be around 15g/L.

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