A novel azo dye, 8-quinolinol-5-azoantipyrine as corrosion inhibitor for mild steel in acidic media

A newly synthesized azo compound, namely 8-quinolinol-5-azoantipyrine (HQAP), was studied as an inhibitor for the corrosion of mild steel in 1M HCl. Results of weight loss and Tafel polarisation measurements show that this compound has fairly good inhibiting properties for steel corrosion in acidic bath, with efficiency around 96% at a concentration of 10−3 M. The inhibition is of a mixed anodic-cathodic nature. Langmuir isotherm is found to provide an accurate description of the adsorption behaviour of the investigated azo compound. Some thermodynamic parameters such as the adsorption heat, adsorption entropy and adsorption free energy have been calculated by employing thermodynamic equations. Kinetic parameters such as the apparent activation energy and pre-exponential factor have been calculated and discussed.