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

－ Relationships between Dissolved Oxygen Concentration and Corrosion of Mild Steel and Copper (1) －

Abstract

The corrosion inhibition efficiencies of the oxygen decreasing treatment for mild steel and copper were evaluated through measuring corrosion rates of test coupons and corrosion potentials of electrodes hanging in the twenty three heat storage water tanks. The results of the evaluation, the corrosion rates of mild steel were reduced following DO concentration decreasing. In case of copper, most of case, the corrosion rates of test coupons showed the tendency of corrosion rate reduction following DO decreasing and the corrosion potentials of copper electrodes were less than 140mV (SSE). But, at two hot water tanks in which less than 0.5mg/L of DO concentration, the corrosion potentials of both copper electrodes increased to 220mV (SSE) and the corrosion rates of test coupons showed higher than the rate at DO saturated water.