On Fri, 02 Jun 2006 19:34:41 +0100, F wrote:

A Google for 'passive stainless steel citric acid kitchen' produced lots
of industrial references:

Sorry, typo on my part - should have been "passivate".

You can do it with citric acid, or with hydrofluoric acid. Don't use
hydrofluoric, it's ****ing toxic in ways you can't even imagine. Nitric
acid might be used, be is too likely to discolour it with iron salts,
unless you're in a careful production environment. Citric acid is easy
though, and safe.

For small stuff, throw it in a pan of warm citric acid and simmer it for
half an hour. For sheetmetal, wipe it over with a spongeful of warmed,
10% (by weight) citric acid solution, as hot as you can handle in rubber
gloves. Leave it for half an hour, then rinse. If you can warm the
metalwork up first (hot air gun?) then it's likely to give a better
result, but you only need it "uncomfortably hand hot", not glowing.

Degrease _throughly_ beforehand, by giving it a good "kitchen
scrubbing", doing your refinishing and polishing, then wiping it down
carefully with isopropanol or acetone on kitchen paper towels (standard
workshop solvents, shouldn't be too hard to find).

The theory
http://www.delstar.com/passivating.htm
http://www.mmsonline.com/articles/100304.html

Practice is probably best described on www.finishing.com

Citrisurf is supposed to be the dead easy improved version.
http://www.stellarsolutions.net/wave.htm