Hexamine as anti-pit agent for mild steel in sulphuric acid medium

Mild steel corrodes very heavily when exposed to dilute sulphuric acid medium. Pitting corrosion takes place on the surface of mild steel in absence of corrosion inhibitor. Hexamine is a long chain amine having nitrogen atom as heteroatom. Hexamine was tested as corrosion inhibitor for mild steel in 0.1 NH2SO4 as corroding medium at 25.0, 30.0 and 35.0 degrees C by weight loss, electrochemical polarization and impedance spectroscopy methods. Hexamine was proved to be a very good anti-pitting agent for mild steel in dilute sulphuric acid medium. Surface study of corroded and un-corroded specimens of mild steel was carried out by Metallurgical Research Microscopy (MRM) and Scanning Electron Microscope (SEM) techniques. Surface study confirms that the adsorption of hexamine takes place through nitrogen atom resulting in the formation of uniform, nonporous, passive film confirmed by decrease in Warburg Impedance (Z(w)), decrease in Faradaic current, increase in capacitive current and significant increase in capacitive loop in Nyquist plot with increase in concentration of hexamine which results in significant decrease in corrosion rate of mild steel in dilute sulphuric acid medium especially eliminating pitting corrosion.