Metal finishing Q&As since 1989

-----

Chromium stripping voltage

Hi, I am trying to determine if a misstep that occurred in the stripping of hard chromium plating from a droop ring made of 13-8 precipitation hardened stainless steel will lead to embrittlement, surface pitting, etc.. The ring was stripped anodically in a sodium carbonate / washing soda [affil links] and sodium hydroxide solution at 12 volts. The process was only supposed to occur at around 4 volts maximum. This part is to be replated and used, however there is concern that the additional voltage may compromise the stainless steel. I can't find how voltage affects hard chromium stripping anywhere! Please help! Thanks :)

Alexandra Kasik
materials engineer - Mesa, Arizona, United States
November 16, 2009

---

Alexandra, We have stripped chrome from various stainless valve steels (21-2N, 21-4N etc) with similar caustic stripper at 6-8 volts. If voltage was to high or time was too long, valve stems would darken up (brown surface under chrome plated area). Parts would simply be repolished to clean off and replated to size. If you have concern about hydrogen embrittlement, you should be able to perform a hydrogen relief bake 375F for 2-4 hrs before and/or after replating. Recommend checking with your customer first about maximum temperature 13-8 PH part can tolerate to avoid over tempering part.

Tim Deakin
North Tonawanda, New York
December 15, 2009