Protection of nickel-chromium steel in sulfuric acid solution by a substituted triazole

Abstract

The corrosion of 12Kh18N10T nickel-chromium steel in 2.0 М H2SO4 (t = 20–100°C) was studied using mass loss, potentiometric, and polarization methods. It was shown that the corrosion resistance of this material in H2SO4 solutions is low, particularly at temperatures close to 100°C. Efficient steel protection in sulfuric acid solutions can be achieved using mixtures of IFKhAN-92 (a triazole derivative) with KI (molar ratio of the components 1: 1), KBr ( 1: 9), or KCNS ( 4: 1) as corrosion inhibitors. Of the IFKhAN-92 formulations studied, the highest corrosion inhibition coefficients are provided by the equimolar mixture with KI, despite an antagonism in the action of its components. Decreasing the concentration of this formulation to 0.005–0.025 mM (depending on temperature) does not considerably decrease the protective effect. Mixed inhibitors based on the substituted triazole protect the metal in the acid solution for at least 8 h. The presence of the inhibitors being studied in the solution considerably increases the contribution of diffusion control to the corrosion process, as indicated by a significant decrease in the activation energy from 60 1 to 35 2 kJ/mol in the presence of these compounds. Steel corrosion occurs in the active dissolution region both in background and inhibited acid solutions. A correlation was noted between the free corrosion potential of steel (Ecor) in an acid solution containing an inhibitor and the protective effect of the latter (): the higher the  value of the inhibitor, the more positive the potential of steel. The corrosion inhibition of stainless 12Kh18N10T steel in H2SO4 solutions by formulations based on IFKhAN-92 results from strong hindrance of electrode reactions on the metal by these compounds in a broad temperature range (up to 100С). The strongest inhibition of electrode reactions on stainless steel is provided by the IFKhAN-9 2+ KI mixture. As a result, it has the maximum efficiency in suppression of metal corrosion. A considerable effect on the characteristics of electrode reactions on stainless steel in background and inhibited acid solutions results from selective dissolution of metal surface components.