The Corrosion Inhibition Effect of Thiourea for Q235 steel in Oxalic Acid Solution

This work is dedicated to exploring the optimum concentration and anti-corrosion mechanism of pickling agent that can effectively remove corrosion products of high-speed railway trains. A commonly used oxalic acid cleaning agent with thiourea was diluted to 5%, 10%, 15%, and 20%. Based on EIS and Tafel tests, we found that thiourea could provide efficient protection for Q235 steel when the diluted concentration was 5%. Meanwhile, thiourea was a modest and mixed corrosion inhibitor for Q235 steel in oxalic acid. SEM observation further proved the above conclusion. According to theoretical calculation, the high E-HOMO, E-binding and low E-LUMO, Delta E values of thiourea stood for the excellent adsorption ability and supreme anti-corrosion performance.