Tetrazolo[1,5-a]quinoline-4-carbaldehyde and its Schiff base on mild steel as corrosion inhibitor in 1M HCl solution: electrochemistry, theoretical and SEM surface analysis

The corrosion inhibition impact of two quinoline derivatives, viz tetrazolo [1,5-a] quinoline-4-carbaldehyde (TQC) and (Z) -5-methyl-N-(tetrazolo [1,5-a] quinolin-4-ylmethylene) thiazol-2-amine (MTQT), has been examined against mild steel in 1M HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, quantum chemical, and scanning electron microscopic studies. The experimental results have showed that TQC and MTQT revealed a good corrosion inhibition and that the inhibition efficiency increases with the increase of concentration of inhibitor to attain 94.54% for TQC and 99.25% for MTQT at 25ppm. Polarization measurements suggest that TQC and MTQT act as a mixed-type inhibitor. A synergism between inhibitors can be observed by polarization measurements. Electrochemical impedance spectroscopy measurements show an increase of the transfer resistance with the inhibitor concentration. Adsorption of TQC and MTQT on the mild steel surfaces in 1N HCl solution follows the Langmuir adsorption isotherm model. Furthermore, quantum chemical calculations have been conducted using B3LYP functional and 6-31G(d,p) basis set to complement the experimental evidences. Copyright (c) 2015 John Wiley & Sons, Ltd.