Abstract
We measured the rest potentials（corrosion potentials）of different metals over 30 days at 50 ℃, 70 ℃, and 90 ℃, while immersed in mother liquors of varying compositions. The metals used for the test pieces were S31600，S31254，S32053，N08354 and N06022 from which evaporators are fabricated. Within those solutions having a composition used in salt production, the effects of the concentration and temperature of the mother liquor on the rest potentials were small and the effects of the concentration of dissolved oxygen（DO）and copper ions in the mother liquor became larger with an increase in the concentration of DO and copper ions. A similar tendency was indicated for the metals used in this study. Thus, to effectively protect metals from corrosion, the concentration of the DO and copper ions in the mother liquor should be controlled. On the other hand, when the DO concentration is greatly reduced, the effects of the copper ions on the rest potentials were small. Thus, it has been suggested that the copper ions accelerate the redox reactions caused by DO.
