Having read your article online concerning aluminum oxide impregnation (February 2003), I am curious. I grit blast aircraft exhaust systems prior to welding repair using aluminum oxide. I use 36 grit on Type 321 stainless steel to remove the baked on combustion products to achieve a clean surface for TIG welding. Am I getting aluminum oxide impregnation when I clean/blast these parts? Keep in mind that I regulate the air pressure to the gun in the cabinet to 60 psi. M.S.
II cannot say with certainty if you are getting any aluminum oxide impregnation; although I think it is certainly possible. Do you perform any other operations following the blasting? If not, there is probably some residual aluminum oxide, although I am not sure that it will cause any welding issues.