PetroStreet

Very often you come across some maltreated SS material. The contamination could be due to contact with CS or may be due to sandblasting with Chloride-laden sand etc.

What is the most viable way to clean such material remembering that nasty acid baths aren't always a desirable option and in fact not an option at all?

Glass Bead Blasting
Garnet Blasting

Please comment.

What's your application?
I do not agree with you that acid cleaning /pickling are not an option. Believe me mechanical cleaning of SS is not effective at all when compared to the advantage of acid treatments.
However, if you just want to go with mechanical cleaning, you then may use glass bead blasting as the first option and then garnet or sand blasting as the second option. You have to consider many precautions when doing blasting operation like the selection of grade and quality of sand / garnet.
Blasting roughens the steel surface which then is less resistive to scale / deposit formation and crevice corrosion.

Contamination of SS with CS or blasting - the best solution is acid treatment /passivation
Mechanical cleaning again on already blasted surface would impair the condition by increasing the surface roughness. I do not recommend.

These are SS air ducts which have already been given a coat of Zinc Phosphate by the contractor which needed to be removed. Bead blasting or Acid Cleaning is not possible at the site.

What's the extent of contamination and the service severity with respect to corrosion? Have you blasted with chloride containing sand?

Then the only option left for you is to perform grit or shot blasting with stainless steel media.

A nice and short article on SS surface finishing http://www.azom.com/details.asp?Article ... d_Blasting