Triazines: Efficient Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution

Five triazines namely Hexahydro-1,3,5-triphenyl-s-triazine (Inh-1), Hexahydro-1,3,5-p-tolyl-s-triazine (Inh-2), Hexahydro-1,3,5-p-methoxyphenyl-s-triazine (Inh-3), Hexahydro-1,3,5-p-aminophenyl-s-triazine (Inh-4) and Hexahydro-1,3,5-p-nitrophenyl-s-triazine (Inh-5) were synthesized and investigated as corrosion inhibitors of mild steel in 1N HCl solution using weight loss, polarization resistance, Tafel polarization and electrochemical Impedance spectroscopy techniques. The inhibition efficiency of the synthesized inhibitors followed the order Inh4 > Inh3 > Inh2 > Inh1 > Inh5. The inhibiting action of triazines was found to depend on electronic nature of functional groups present in triazines. Potentiodynamic polarizations suggest that triazines are mixed type in nature. Electrochemical Impedance spectroscopy was also used to investigate the mechanism of corrosion inhibition. Thermodynamic parameters were also calculated to know the mechanism of the inhibition. AFM is used to know the surface roughness of the mild steel sample with and without inhibitors.