The final operation after fabrication or heat treatment is cleaning to remove
 surface contamination and restore corrosion resistance of the exposed
 surfaces.  Degreasing to remove cutting oils, grease, crayon markings,
 fingerprints, dirt, grime and other organic residues is the first step.

Degreasing:  Non-chlorinated solvents should be used in order to avoid leaving
 residues of chloride ions in crevices and other locations where they can
 initiate crevice attack, pitting, and/or stress corrosion later on when the
 equipment is placed in service.

Machined components:  After degreasing, machined components are sometimes
 "passivated" in 10% nitric acid.  Nitric acid does not corrode the surface of
 stainless steel.  Nitric acid does thicken the natural oxide film and is
 especially beneficial to cross sections exposed in machining operations.

Fabrications:  After degreasing, metallic surface contaminants such as iron
 embedded in fabrication shop forming and handling, weld splatter, heat tint,
 inclusions and other metallic particles must be removed in order to restore
 the inherent corrosion resistance of the stainless steel surface.

Nitric HF pickling, (10% HNO3, 2% HF at 120 to 140F), is the most widely used
 and effective method removing metallic surface contamination.  Pickling may 
 be done by immersion or locally using a pickling paste.

Electropolishing, using oxalic or phosphoric acid for the electrolyte and a
 copper bar or plate for the cathode can be equally effective.  Electro-
 polishing may be done locally to remove heat tint alongside of welds or over
 the whole surface.

Both pickling and electropolishing remove a layer several atoms deep from the
 surface.  Removal of the surface layer has the further benefit of removing
 surface layers that may have become somewhat impoverished in chromium during
 the final heat treatment operation.

Glass bead, walnut shell and CO2 pellet blasting are very effective in
 removing metallic surface contamination without damaging the surface.  It is 
 sometimes necessary to resort to blasting with clean sand to restore heavily
 contaminated surfaces such as tank bottoms, but care must be taken to be
 certain the sand is truly clean, is not recycled and does not roughen the
 surface.

Stainless steel wire brushing or light grinding with clean aluminum oxide
 abrasive discs or flapper wheels are helpful.  Grinding or polishing with
 grinding wheels or continuous belt sanders tend to overheat the surface
 layers to the point where resistance cannot be fully restored even with
 subsequent pickling.

More information on cleaning and finishing may be found in:
    "Heat Treating, Cleaning and Finishing", Metals Handbook, 8th Edition,
      Vol. 2 in the section entitled "Heat Treatment of Stainless Steels and
      Heat-Resisting Alloys".

     ASTM A 380, "Recommended Practice for Cleaning and Descaling Stainless
      Steel Parts, Equipment and Systems", ASTM, 1916 Race Street,
      Philadelphia, PA  19103.

     Tuthill, A. H., "Fabrication and Post Fabrication Cleanup of Stainless
      Steel", NiDI literature, Item 10 004.

     Pettibone, J. S., "Burgers, Fries, Coke, and Stainless Steel", NiDI
      literature, Item 10 009.

     AISI, "Cleaning and Descaling Stainless Steel", NiDI literature, Item
     9 001.