Studies on Some Ionic Liquids as Corrosion Inhibitors on 6061 Al-15 Vol. Pct. Sic(P) Composite in Acidic Media

Abstract

The thesis entitled “Studies on some ionic liquids as corrosion inhibitors on 6061 Al-15 vol. pct. SiC(P) composite in acidic media” brings about detailed studies on the corrosion behavior of the composite and also the inhibition studies in hydrochloric acid and sulfuric acid media at different temperatures using electrochemical techniques like potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS). Lately, the composites have replaced pure aluminum in wide variety of applications ranging from house-hold to aerospace applications. The increased strength to weight ratio, density, reduced coefficient of thermal expansion and other valuable attributes make it an engineer’s choice over pure aluminum. As a misery to this choice, low corrosion resistance as compared to pure aluminum is the matter of concern among the corrosion engineers. Therefore, study of corrosion rate and developing new methods to control corrosion is inevitable. SiC particle reinforced composites are prone to micro-galvanic corrosion in the presence of strong electrolytes. Bearing in mind the ‘go-green’ trend in recent research, four ionic liquids namely, [OPEIm+][Br−], [MPOEIm+][Br−], [OPEBen+][Br−], [MPOEBen+][Br−] were synthesized, characterized and studied for their corrosion inhibition effect on the composite. The activation parameters for the corrosion process and the thermodynamic parameters for the adsorption of inhibitors on the composite surface were evaluated. Surface analyses of the freshly polished surface of the composite and that of the corroded samples in the presence and absence of inhibitors were carried out by scanning electron microscopy (SEM) and the surface compositions were determined by energy dispersive X-ray (EDX) analyses. The synthesized ionic liquids acted as efficient corrosion inhibitors in both the acidic media under study at definite concentrations. [MPOEBen+] [Br−] showed higher efficiency at relatively lower concentrations owing to its macromolecular structure and high electron density, as compared to rest of the ionic liquids. The inhibition was found to be of mixed type with predominant cathodic control. The inhibitors were adsorbed on the composite surface predominantly through chemisorption, following Langmuir adsorption isotherm. Plausible inhibition mechanism is also proposed in the thesis.