Q. I am interested in a replating cycle for chrome over nickel. I know we have to strip the chrome from the nickel prior to replating, but can you provide a procedure for doing this? —H.D.
A. As you are probably aware, plating chromium on chromium is possible but usually very difficult. If your part is simple, you might be able to remove the chrome by grinding, but in almost all situations it is easier to strip the chrome chemically or anodically.
One procedure for doing so consists of placing the parts in diluted hydrochloric acid (125 mL/L) and heating the solution to approximately 110-125°F. You may see violent hydrogen gassing when the parts are initially placed in this solution, so the process must be monitored at all times.
Once gas evolution has ceased, rinse the parts thoroughly. Your nickel layer most likely will be passivated. You should activate it by dipping the parts in a 200 mL/L hydrochloric acid solution, rinse thoroughly and than proceed to the chromium plating step.