Some acids can be used for passivating SST like Citric and Nitric. Some like the hydrochloric in Muriatic will strip the passive layer away and also strip the surface chrome away too leaving rust-worthy surface behind. Some of the bad acids can be found in food.
To expand on Cliff's comments, in generally mineral acids like sulfuric & hydrochloric to name a few should not be used on SS, although some like nitric & phosphoric are perfectly fine. Also in general organic acids like citric & oxalic are perfectly fine to use on SS.
I'm thinking the gray film is the talcum powder which isn't soluble in water, but is in acidic solution. I would probably wipe as much off as possible, then hit with like starsan or other mild acid cleaner solution (without talcum) and wipe again.