Acidic-Functionalized Ionic Liquid as Corrosion Inhibitor for 304 Stainless Steel in Aqueous Sulfuric Acid

The corrosion behavior of three acidic media, 98% sulfuric acid, 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate ([BsMIM]­[HSO4]) and 1-(4-sulfobutyl)-3-methylimidazolium tetrafluoroborate ([BsMIM]­[BF4]), was studied by electrochemical impedance spectroscopy (EIS) and Tafel plots. It indicated that the corrosion mechanism is controlled by charge transfer. And the two acidic-functionalized ionic liquids (AFILs) exhibited lower corrosion rate. On the basis of the electrochemical corrosion results, the inhibition ability of AFILs in 1.0 M sulfuric acid toward 304 stainless steel was investigated at various concentrations and temperatures using gravimetric measurement, combined with the characterization of 304SS surface morphology by scanning electron microscopy (SEM). The results showed that the two AFILs act good as inhibitors, especially at low temperatures. The inhibition efficiency increases with the inhibitor concentration, and decreases sharply above 60 °C. The thermodynamic parameters suggested that the adsorption of AFILs on the 304SS surface occurred by physical and chemical adsorption. And the corrosion inhibition mechanism is proposed.