A New Mechanism for the Inhibition of SA106 Gr.B Carbon Steel Corrosion by Nitrite in Alkaline Water

Abstract

The purpose of this study was to investigate the composition of oxide films formed on SA106 Gr.B carbon steel in nitrite solutions at 35 °C for 1000 h. The product of the reduction of nitrite during the corrosion inhibition process was also examined. The X-ray photoelectron spectroscopy results revealed that a thin Fe3O4 film was formed and ammonium ions were adsorbed on the outermost surface of the oxide film. The presence of ammonium ions was also demonstrated by ion chromatography. These results indicate that nitrites are reduced to ammonium ions, which in turn promotes the formation of the protective Fe3O4 film.

Keywords

• carbon steel
• nitrite
• corrosion inhibition
• polarization
• X-ray photoelectron spectroscopy
• passive film