With copper matrix? If so, the trigger may not be in place. Increase the area of the trigger iron sheet and increase the temperature. Of course, we should also know the composition of copper. Some copper alloys cannot be electroplated.

In fact, there are several reasons for not plating: poisoning of plating solution, insufficient temperature, inaccurate pH, insufficient activation, or problems with matrix materials.

Even if the oil removal is not complete, there should still be a coating. At best, the coating is incomplete or the adhesion is not good, but it will never be electroplated.

If it can be plated before, but suddenly it can't be plated, it is a problem of bath parameters or pretreatment, at least there will be no problem with the formula.

If it's most, it's another matter.