Inhibitory effect of thiamine salts on steel corrosion in an acidic environment: an experimental and theoretical approach

Abstract

The effectiveness of thiamine hydrochloride and thiamine pyrophosphate as corrosion inhibitors for steel in 1.0 M hydrochloric acid medium was assessed through electrochemical techniques supported by theoretical calculations. The results indicate that both compounds exhibit significant corrosion inhibition efficiency in HCl, with thiamine hydrochloride providing better protection for the steel surface than thiamine pyrophosphate. According to the results obtained from electrochemical impedance spectroscopy, at a concentration of 5 × 10⁻³ M, the inhibition performance of thiamine hydrochloride reached 87.87%, whereas thiamine pyrophosphate exhibited an efficiency of 85.28%. Potentiodynamic polarization measurements reveal that both thiamine hydrochloride and thiamine pyrophosphate act as mixed-type inhibitors. The inhibition ability of the compounds tends to decrease with increasing temperature, indicating a reduction in the stability of the adsorbed protective layer on the steel surface at elevated temperatures. Adsorption isotherm analysis suggests that the adsorption behavior of thiamine hydrochloride and thiamine pyrophosphate molecules on the steel surface is well described by the Langmuir adsorption model. Surface morphology observations show that the steel sample subjected to immersion in a thiamine hydrochloride solution exhibits significantly less surface damage compared with the sample in the presence of thiamine pyrophosphate. Theoretical analysis and molecular dynamics simulations further indicate that thiamine hydrochloride has a stronger interaction and better surface coverage on the Fe surface than thiamine pyrophosphate. These findings are consistent with the experimental data, confirming that thiamine hydrochloride outperforms thiamine pyrophosphate in mitigating the steel corrosion process in hydrochloric acid medium.