Abstract
The technology of non-toxic corrosion inhibitors developed as a replacement of chromate in cooling water treatment was reviewed. Polyphosphate and phosphonate react with mother metal ion to form a protective film at anodic sites. On the other hand they form a protective film by precipitation with zinc ions and / or calcium ions at cathodic sites depending on their concentration. Acryl acid based polymer or maleic acid based polymer used as scale inhibitor enhances the effectiveness of cathodic inhibitors for carbon steel, and also made possible to increase the cycle number of concentration in cooling water and to decrease the total amount of phosphate in effluent water. The developments of green inhibitors, scale inhibitors for silica scale, non-chemical water treatment devices, and so on are expected in future.
