Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Randy Taylor, Advanced Tooling Corporation
Chrome Stripping from Steel without Damaging Substrate
Q. Hello! I have an antique sword that some fool has chromed. It's carbon steel, and has fairly delicate engraving and etching on the steel which I don't want to damage. Is there some method of electrically stripping it without acids that will eat the steel?
I tried a local plater who offered to bead blast it. Right.
I have access to hazmat disposal.
A. Good call, avoiding the "bead blaster"!! I see this far too often. People mistakenly assume "grit blasting" is the fast way to remove decorative chrome. This of course, is not the case if you value the base metal.
Can you ascertain visually if chrome is the only coating? It would be plated directly on the steel and may have worn or broken through areas which would appear as base metal? Or might there be nickel or copper nickel in-between? Nickel would appear visually as a light bronze color, and of course copper is copper color.
Stripping metallic coatings is challenging, especially with non-acids. But here are a few tips.
Easy enough to remove the chrome in a NaOH and water mix (NaOH 4-10 oz./gal. of H2O.) with reverse DC current at 4-6 VDC. This strip chemistry is safe for ferrous alloys and should not affect base metal. If chrome all you have to deal with, you're done.
If you have subsequent layers of nickel and or Ni/copper, these would be more difficult to remove. For best results use a cyanide based stripper. From old notes, a mix of Ammonium bifluoride, NaCN, NaOH, m-nitrobenzene sulfonic acid, also reverse current 3.5-5.5 VDC. Good luck finding a local shop that still uses cyanide.
If you can verify the exact steel alloy of your sword, you might be able to get better information direct from the chemical manufacturer that makes up the strip chemicals.
Example: Enthone, West Haven, CT. email@example.com or Hubbard-Hall Inc. 563 S. Leonard St. Waterbury, CT. www.hubbardhall.com Maybe we'll see you and your sword on "Antiques Roadshow" some day! Good luck. R. Taylor