Inhibition of Type 304 Stainless Steel Corrosion in 2 M Sulfuric Acid by Some Benzoazoles—Time and Temperature Effects

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Abstract
2-methyl benzoazole and 2-mercapto benzoazole derivatives were investigated as corrosion inhibitors for Type 304 (UNS S30400) stainless steel in 2 M sulfuric acid (H2SO4) solution using weight loss, gasometry, and alternating current (AC) impedance techniques. Effect of immersion time and temperature were studied. The observed inhibition efficiency was found to depend on the heteroatom and type of side group. The efficiency of 2-methyl benzoselenazole (MBS), 2-mercapto benzoimidazole (CBI), and 2-mercapto benzothiazole (CBT) were independent of immersion time. However, MBS presented an efficiency of ~ 90% at 45°C and caused a decrease in the activation energy of the corrosion process. Similarly, CBI and CBT had high efficiencies that remained almost unchanged at temperatures between 25°C and 55°C, but their activation energies increased slightly compared to that in their absence. Chemisorption of inhibitor molecules was used to explain the results of this study.

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