Corrosion inhibition of iron in 1M HCl by 1-phenyl-5-mercapto-1,2,3,4-tetrazole

The mode of corrosion inhibition of pure iron due to 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT) in molar HCl is studied through weight loss and electrochemical steady-state experiments. From the comparison of results with those obtained using other “tetrazole” -type organic compounds, it is shown that PMT is the best inhibitor and its inhibition efficiency becomes 98% at 2 × 10−3M. Polarisation measurements show that PMT is a mixed-type inhibitor. PMT acts on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. The PMT appears to function through the general adsorption mode following the Langmuir adsorption isotherm model. The effect of temperature on iron corrosion behaviour in both 1M HCl and 1M HCl + 10−3M PMT have been studied. The inhibition efficiency of PMT is temperature-independent in the range 20–45°C. The associated activation corrosion and adsorption energy has been determined.