Maintaining Environment Nondestructive To Metal Patents (Class 422/7)
- Using organic compound having phosphorus (Class 422/15)
- Using organic nitrogen compound other than ammonium salt (Class 422/16)
- Using organic carboxylic acid or salt thereof (Class 422/17)
- Using inorganic silicon or phosphorus compound (Class 422/18)
- Using heavy metal or compound thereof (Class 422/19)