Exploration of (S)-4,5,6,7-tetrahydrobenzo[d]thiazole-2,6-diamine as feasible corrosion inhibitor for mild steel in acidic media

• (S)-4,5,6,7-Tetrahydrobenzo[d]thiazole-2,6-diamine (TDA) was investigated as a corrosion inhibitor for mild steel.
• Surface studies reveal the adsorption of TDA on the mild steel surface.
• TDA adsorption on mild steel is a spontaneous process and classical Langmuir adsorption is followed.
• DFT calculations showed the optimized TDA molecular structures and other quantum chemical parameters.

This study deals with the possibility of (S)-4,5,6,7-tetrahydrobenzo[d]thiazole-2,6-diamine (TDA) as a prospective corrosion inhibitor for mild steel in 1 M hydrochloric acid (HCl) medium. The inhibition characteristics by means of weight loss, Tafel polarization and electrochemical impedance spectroscopic methods are reported. Results showed that the inhibition efficiencies increase with increasing concentration and while increasing temperature it shows negative effect. Associated equilibrium adsorption constant and other thermodynamic parameters suggested that TDA follows comprehensive adsorption behavior in blocking the active corrosion sites. Morphological investigation of corrosion sites was carried out by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies, which reveal that the inhibition occurs due to the adsorption of the inhibitor molecules on the metal surface.

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