Water-soluble triazolylpurine derivatives as corrosion inhibitors for mild steel in 1 M HCl solution

Six water-soluble 2-triazolylpurine derivatives and one 2,6-bistriazolylpurine derivative were identified as corrosion inhibitors for mild steel in aqueous 1 mol/L HCl solution. Among them highest inhibitory activity exhibited 2,6-bistriazolylpurine derivative reaching up to 93% according to electric impedance spectroscopy and 98% according to gravimetry at 10^-3 mol/L. Whereas, in the presence of 6-methylamino-2-triazolypurine derivative an inhibition efficiency as high as 95% at 10^-3 mol/L was achieved, according to Tafel polarization. In most cases inhibition efficiency increased at higher inhibitor concentrations. Molecular orbital densities and relevant parameters from quantum chemical calculations showed little difference among target compounds. It is supported by experimental results of high inhibitory efficiency of approximately 90% or higher for all triazolylpurine derivatives at the highest tested concentration (10^-3 mol/L) with varying rates of efficiency reduction at lower concentrations.