METAL HEAT TREATMENT, carbon stopoff paste for carburizing
Rorschach, the reason for the discrepancy is my typing before thinking in this case! Yes, your Kolene licensee is quite correct, you can't use copper as a stop-off, since it will be attacked by the salt. So thank you very much for correcting me! As much as I hate being wrong, I hate even more misleading folks.
From a Kolene SBN brochure I have (actually the proceedings from an SBN seminar in October of 1985) a Dr. Mueller noted that nickel plating can be used as a stop-off. I believe he meant electrolytic nickel as he also reported that they were working on using an electroless nickel formulation to selectively nitride, but were still developing it at that time. Since Mueller is identified as the Executive Managing Director of Durferrit, I believe him.
Thanks again, Stan!