The mechanism of corrosion inhibition by phosphate-based cooling system corrosion inhibitors has been studied by both electrochemical and chemical techniques. Electrochemical studies have been conducted by Raistrick,1 Shome,2 Lamp and Eliassen,3 Hatch,4 and Nathan.5 All of these works indicate that polyphosphates and aminotrimethylene phosphonate are cathodic inhibitors. Chemical experiments have been conducted by Puckorius,6 Hatch,4,7 and Lamp and Eliassen.3 These workers found the formation of protective films comprised of iron, inhibitor, and other cations.
This study reports the results of an investigation in which corrosion inhibition, conductivity, and sequestration data were used to study the mechanism of corrosion inhibition by phosphate-based cooling system corrosion inhibitors in a carbon steel cooling water system.
The phosphate-based inhibitors selected for this study were sodium hexametaphospate (SHMP), sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), sodium orthophosphate (o-PO4), aminotrimethylene phosphonate (ATMP), and hydroxyethylidiene diphosphonate (HEDP). Corrosion...
