Synthesis and evaluation of isatin derivatives as corrosion inhibitors for Q235A steel in highly concentrated HCl

A series of inhibitors—isatin derivatives aimed at anticorrosion of Q235A steel—was synthesized. The molecule structures were analyzed by NMR and MS. The inhibition on the corrosion in a concentrated HCl solution as high as 3 M was studied by weight loss, molecular simulation, and potentiodynamic polarization. The results indicate that isatin derivatives act as mixed type (cathodic/anodic) inhibitors. Several compounds were investigated in the formulations, during which compound 6 shows 95.5 % inhibition efficiency under the concentration of 100 mg/L accompanied by urotropine and 1,4-dihydroxy-2-butyne.