Metal finishing Q&As since 1989
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Passivating stainless steel sculpture
June 3, 2011
I am a sculptor working out of my garage in Dedham, Ma.
Lately, I have begun working with s/s and noticed that I get small rust spots in areas that have been welded or hit by spatter from my MIG welder.
A s/s fabricator told me of a process called passivation- where he brushes on a water soluble acid that cleans the surface of any iron particles. No electrodes are involved- just brush it on- wait 30 min and wash it off with a hose/water.
Can anybody inform me of where I can buy passivating acid?
I need to install this sculpture next week (6/8/11!!!)
Sorry for the last minute request!
Thanks!
Artist/Sculptor - Dedham, Massachusetts, USA
What you are describing is called pickling paste. You should be able to get it from your local welding supplier.
Jon Barrows, MSF, EHSSC
GOAD Company
Independence, Missouri
June 7, 2011
10% citric acid solution.
If possible immerse the item, otherwise brush on and keep it wet with solution for about 15-30 mins then rinse off with water.
Alternately, clean the spots with shotblasting, sanding, filing, brushing (as appropriate to size etc) and leave dry indoors for about 24 hours and it will self passivate.
You are trying to get the Cr oxide layer to reform. It will happen naturally (if the surface is cleaned well), or you can hasten it.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
June 8, 2011
Citric-based passivation pastes are available. Nitric-based pickle pastes work too but are hazardous to work with.
Passivation is especially important in weld heat affected zone (HAZ) areas because the change in alloy structure due to the temperature decreases the corrosion resistance.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
June 9, 2011
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