Two other common things that metal finishers used to do:
1. Use glacial acetic acid, diluted half and half and be DAMNED careful, this is treacherous stuff. Wear neoprene gloves. WATCH the action of scale removal. Do not let it progress beyond what you want to remove. This must be done outdoors. Wear protective clothing and an eye shield from your polishing setup. Neutralize with household ammonia and wash off thoroughly. (Glacial acetic acid is available from photo chemical suppliers, and is a super concentration.) Follow directions for safe handling. Keep a copy in your OSHA file.
2. Use dilute sulphuric acid. When diluting, follow instructions about adding acid, etc. Wear neoprene gloves, a rubber or neoprene apron, shoe protection, eye protection and do it outdoors. When the desired action is complete, neutralize with household ammonia.
3. After each of the above treatments, you should immerse the blade in boiling water, to which a small amount of household baking soda has been added, just to make certain that the chamical action is arrested. Boil 5 min., remove and air dry.
