The use of amines as steel corrosion inhibitors in butanol-gasoline blends

Abstract

Butanol is an interesting component used for blending gasoline fuels. However, the polar nature of butanol allows the solubility of water and ionic compounds in butanol-gasoline blends (BGBs) making them aggressive to mild steel. Amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentaamine, morpholine, piperazine, and hexamethylenediamine, were tested as corrosion inhibitors for mild steel in BGBs. Additionally, the influence of the acetic acid and sodium chloride concentrations on the inhibition efficiency was examined. Electrochemical impedance spectroscopy andpotentiodynamic polarization were employed for the measurements, complemented by static immersion testing and an XPS surface analysis. The highest inhibition efficiency was demonstrated for diethylenetriamine, triethylenetetramine, andhexamethylenediamine, achieving a value of 95 % or more at aconcentration of 100 mg/L. The formation of ionic pairs involving protonated amines andchlorides was also confirmed. The XPS analysis revealed a very thin passive layer of iron oxides, which may form in the presence of amines, protecting mild steel in BGBs.