Electrostatic adsorption of hexamethylenetetramine as a corrosion inhibitor for FeTi1.88C2.35 cast iron in electrolytic acid solution

Abstract

The adsorption process of hexamethylenetetramine (HMTA) as a corrosion inhibitor for an elaborated FeTi1.88C2.35 alloy presenting a lamellar pearlitic phase was investigated in 0.5 M HNO3 at different temperatures, by means of potentiodynamic polarization and linear polarization resistance. The characterization of the ferrous material was done by using X-ray diffractometry and scanning electron microscopy coupled with energy dispersive analysis X-ray. The temperature effect on the electrochemical behavior with various concentrations of HMTA was examined in the temperature range 293–323 K. HMTA preserves its inhibitive power against the corrosion of the studied alloy, even if its efficiency is slightly reduced at high temperature. The electrode processes are not affected by the rise of temperature. Quantum chemical calculations were also performed to determine some electronic properties of the molecule in water, in order to correlate between the inhibitive effect and electronic structure of neutral and protonated HMTA in aqueous acid solution. Physical interaction between HMTA molecules and the cast iron surface was suggested by the thermochemical and theoretical parameters.