Synergistic effect of Mannich base and sodium tungstate as corrosion inhibition for N80 steel

Abstract

The corrosion inhibition effect and adsorption behavior for N80 steel in HCl solution were investigated by using electrochemical method and scanning electron microscope, meanwhile, the corrosion inhibition mechanism of inhibitors was analysed from the point of view of the thermodynamic. The results indicate that when Mannich base is added into HCl solution, the charge transfer resistance increases, thereby the corrosion rate of metal surface is reduced. When Mannich base is compound with sodium tungstate, the saturated adsorption capacity of inhibitors on metal surface increases, and the corrosion resistance of N80 steel in HCl solution increases significantly, showing a good synergistic effect. When the molar ratio of Mannich base to sodium tungstate is 1:1.5, the highest inhibition efficiency can reach 99.65%. The adsorption of inhibitors on the surface of N80 is in accordance with the Langmuir adsorption model, and it mainly belongs to chemisorption. The process of adsorption on N80 surface is spontaneous and irreversible endothermic reaction.

Keywords

• electrochemistry
• complexe
• enthalpy
• corrosion
• synergistic effect