plating, anodizing, & finishing Q&As since 1989
Electropolishing solution for stainless steel
The only available source we currently have for a solution for the electropolishing of stainless steel was from The Canning Handbook [affil link to this on eBay, Amazon, AbeBooks], which proved to be a disaster. The solution contained a large amount of water, sulfuric and phosphoric acid. The passivation was sodium dichromate and if I remember correctly, nitric acid.
Can you help us with making up another type of solution which can do a better job? We are currently using a solution which is purchased locally in South Africa, and seems to work well, but is expensive and the demand for this type of work has increased to the extent that we are having to increase the size of our tanks. The cost however would be excessive. The solution we are using now is dark green in colour and has no passivation afterwards. Do you have any idea what this could contain. We would like to make up our solution using locally available chemicals. Can you help.John Mattisson
I have seen nitric-phosphoric acid mixtures that are dark green although I don't know why; and I also know that a lot of dissolved nickel will turn any acid dark green because that's the color of nickel ions.
There is pretty good treatment of electropolishing solutions for stainless steel in the Metal Finishing Guidebook, the Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon affil links] , and ASM's Metals Handbook, all listed on our "must-have" booklist.
But you should realize that when you buy proprietaries you are not just buying chemicals, you are buying know-how by the gallon. You already tried formulating the solution yourself and you called the result "a disaster" and you had to passivate afterwards anyway; then you tried proprietary chemicals, and that approach "seems to work well" while also obviating the need for passivation. I might suggest thinking twice before deciding the cost is "excessive"
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Hi John , I suggest that you e-mail Team Metal Finishing in Georgia , Dan Weaver is the contact , these people have just entered into a joint venture agreement to market internationally an electropolishing process developed in Australia , that has to be seen to be believed , the electrolyte is claimed to be almost Benign , they exhibited for the first time at Sur - Fin recently in Cincinatti they are well worth investigating . regards John . C . Tenison - Woods
John Tenison - Woods
- Victoria Australia
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