Synergistic effect of different Zn salts with sodium octanoate on the corrosion inhibition of carbon steel in cooling water

Abstract

The corrosion inhibition of carbon steel was investigated in cooling water containing sodium octanoate (Oct), Zn-salts or blends of Oct-Zn salts. The weight loss and the potentiodynamic polarization methods were applied. ZnCl2, ZnSO4 and Zn (NO3)2 were studied. The results showed that Oct-Zn salt blends exhibited higher corrosion inhibition efficiency than either Oct or Zn Salts added separately to the cooling water suggesting a synergistic interaction between Oct and the Zn-salts. The polarization results revealed that these blends act as mixed-type inhibitors with three dominant anodic inhibition. The inhibition efficiency of Zn-salts in the absence and presence of Oct was found to decrease in the order Zn (NO3)2 ZnSO4 ZnCl2. Optical microscopy and infrared spectroscopy were used to study the protective action of the films formed on carbon steel in Oct-Zn salt blends. The role of Zn anions and the synergism behavior were discussed.