Corrosion Inhibitions of Mild Steel and Copper by Oxygen Reducing Treatment Using Sealing Materials for Water Surface in Open Heat Storage Water System

－Cause of Copper Corrosion Potential Increasing and Countermeasures for Its Decreasing (2)－

Abstract

The corrosion potential of copper electrodes increased to 220mV (SSE) and green rusts were produced on them in some hot water tanks in which DO concentration had been kept less than 0.5mg/L by the oxygen decreasing treatment. It was estimated that the cause of the potential increasing might be induced by microorganism because of finding the potential reduction by dosing the biocide in the hot water. After examining the corrosion potential decreasing methods for copper electrodes to inhibit pitting corrosion, the potential of the green rusted copper electrode was decreased by the reduction of the green rust with the hydrazine series water treatment chemicals and the reduced copper electrode showed immunity to the potential increasing after that. The copper potential decreasing was also observed by injecting the chemicals in the hot water.