Effects of heat treatment on the electrochemical corrosion behaviour of aluminum alloy AA3003 in an aqueous acid media

Okeoma Kelechukwu B¹, Owate Israel O²*, Oguzie Emeka E³, Mejeha Ihebrodike M¹.

¹Materials Science Group, Department of Physics, Federal University of Technology, Owerri, Nigeria.

²Materials Science Group, Department of Physics, University of Port Harcourt, Nigeria.

³Electrochemistry and Materials Science Research Unit, Department of Chemistry, Federal University of Technology, Owerri, Nigeria.

*Corresponding Author E-mail: owateio@yahoo.com

Accepted 18 August, 2012

Abstract

The effect of heat treatment and quenching regimen on the electrochemical corrosion behaviour of aluminium alloy AA3003 in 0.1M H₂SO₄ was studied by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Three different specimens (untreated, air-quenched and oven-quenched) were investigated. Polarization results show that all the specimens underwent active dissolution, with no distinctive transition to passivation, although heat treatment was observed to shift the corrosion potential towards more cathodic values and increased the rates of the cathodic and anodic partial reactions of the corrosion process. The impedance spectra for all the specimens comprised a high frequency capacitive loop and an inductive loop at low frequency and reveal lower values of the charge transfer resistance for the heat treated specimens. All of the results indicate that heat treatment diminished the corrosion resistance of AA3003 in 0.1M H₂SO_4, without modifying the mechanism of corrosion. The corrosion resistance decreased in the order; untreated > air-quenched > oven-quenched. This trend has been correlated with the phase constituents of the different specimens as determined from x-ray diffraction (XRD) and scanning electron microscopy (SEM).

Keywords: AA3003, heat treatment, quenching, acid corrosion, electrochemical measurements.

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