7125Descaling and Pickling

After the heat treatment removal of oxide film, which is more tenacious and adherent than compared to stainless steel can be done chemically or mechanically. Chemical treatment may consist of molten caustic descaling salt treatment followed by nitric-hydrofluoric acid bath mixtures (20-25% nitric acid plus 3-5% hydrofluoric acid) at 120-160°F. For Ni-Mo alloys, since they do not contain any chromium, it is very important not to leave the material in the acid bath for more than 60 s followed by an immediate water rinse. This should be repeated as necessary. If sulfuric-hydrochloric acid baths are used, then this precaution is not that critical for Ni-Mo alloys.

Sand, shot, or vapor blasting can also be used for descaling with proper care.

0 0

Post a comment