Triazolothiadiazine derivatives as corrosion inhibitors for copper, mild steel and aluminum surfaces: Electrochemical and quantum investigations

Abstract

The corrosion inhibition activity of triazolothiadiazine derivatives namely 1-(6-(4-nitrophenyl)-7H[1,2,4]triazolo[3,4-b],[1,3,4]thiadiazine3-yl)ethanol (NTTD) and 6-phenyl-3-(triflouromethyl)-7H-[1,2,4]triazole[3,4-b]thiadiazine (FTTD) was examined on copper (Cu), mild steel (MS) and aluminum (Al) in different aggressive media (borate buffers of pH 10.4 and 8.4 for Cu; 1.0 M HCl and 1.0 M NaOH for MS; 1.0 M NaCl for Al). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used and results obtained from both techniques complement each other. CV results showed that the compounds act as mixed type inhibitors for Cu-surface. Impedance spectra of Cu, MS and Al-surfaces in the presence of NTTD and FTTD were characterized as charge transfer controlled. Different parameters obtained from potentiodynamic polarization and impedance data revealed increase in the corrosion protection with inhibitor’s concentration and followed a stable and spontaneous chemisorption mechanism in all aggressive media. Adsorption data from both CV and EIS fitted well to the Langmuir adsorption isotherm. Among both compounds; FTTD has shown better corrosion protection activity in all aggressive media. In general, compound FTTD showed better inhibition efficiency at pH 8.4 among all aggressive media. Different quantum chemical parameters were calculated from DFT/B3LYP based on 3-21G by using Gaussview 03 which further supported the experimental results.