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Abstract:

Purpose – The paper seeks to find out new eco-environmentally friendly surface treatments based on vanadate compounds as alternatives to the process involving toxic chromates for the corrosion protection of aluminium alloys.

Design/methodology/approach – A treatment process in which the surface was etched prior to vanadia treatment is being proposed. The process involves cleaning, etching in potassium hydroxide followed by treatment in vanadia prepared by sol-gel method. The effect of surface preparation prior to vanadia treatment on the corrosion resistance of AA6061 T6 in 3.5 per cent NaCl solution was measured using AC impedance spectroscopy and DC polarization techniques. Surface examination was performed by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).

Findings – It has been shown that the etching process prior to vanadia treatment enhanced formation of a uniformly distributed compact surface V-rich Al-oxide film of smooth appearance and inhibited the active surface sites and thereby preventing localized corrosion.

Originality/value – Vanadate conversion coatings seem very promising as alternatives to toxic chromating for the corrosion protection of aluminium alloys in NaCl solution.

Keywords:

Alloys, Corrosion protection, Surface treatment, Thin films

Article Type:

Research paper

Article URL:

http://www.emeraldinsight.com/10.1108/00035590610678947

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