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.