What if the cotton core in the machine is plated with nickel and copper together?

Adding reducing agent, and then adding na2s for precipitation. If the treatment process is improper, the nickel plating and copper plating on cotton core will be treated together, which will cause the nickel layer to peel off and delaminate. The only solution is to add reducing agent and na2s precipitation. If the dissolution is not obvious, it can be heated slightly. When bright copper enters bright nickel, it can be activated with hydrochloric acid, and it can be solved by bathing in time.