Has anyone had problems with stainless lugs rusting. The last frame I finished, I went to a 220 grit aluminum oxide brushed finished and after 2-3 months the lugs have a light surface rust.
It's also important to keep all of the abrasive rolls, sand paper, scotch brite & etc that you use on stainless parts completely separate from what you're using on the non stainless tubes and parts. Otherwise, its very easy to carry tiny bits of metal over and embed it into the surface of the stainless.....which then later rusts, etc.
When stainless has been worked (filed, sanded,welded, etc) and you want to restore the surface to it's most corrosion resistant state you need to "pickle" or passivate it. This is done with an acid etch that restores the chromium in the alloy to the surface. McMaster-Carr Not saying that the above advice regarding contamination is not important as well. Not many builders as experienced in stainless as Dave Anderson.
The 5% citric solution is all the passivation the alloys used on bikes need.
If you passivate the 410 type steels (most "stainless" tubes) with a standard pickling gel they will need de-smutting afterwards, either mechanically or with a solution of dichromate in sulphuric acid. The former is OK for general surface prep but the latter works best if you are bonding to the steel.
For lugs of 304 or similar alloy the passivation gel won't need de-smutting but you will end up with a matte surface.