Synergistic corrosion inhibition effects of quaternary ammonium salt cationic surfactants and thiourea on Q235 steel in sulfuric acid: Experimental and theoretical research

The corrosion resistance of Q235 steel treated with pure thiourea, dodecyl trimethyl ammonium bromide (DTAB), dodecyl dimethyl benzyl ammonium bromide (DDBAB), and their mixture (i.e. DTAB-Thiourea, DDBAB-Thiourea) in sulfuric acid was studied. Results showed that DTAB-Thiourea and DDBAB-Thiourea have strong synergistic effects (4.86 and 5.99) and could inhibit corrosion by 93.37% and 94.98%, respectively. These effects are attributed to a decrease in the steric hindrance due to changes in the molecular adsorption mode of the corrosion inhibitors. The adsorption forms of all inhibitors on the steel surface were investigated and explained using density functional theory.