Permanganate - Based Hybrid Nano-Conversion Coating on Aluminium

Abstract

The present work investigates a hybrid nano-coating based on permanganate/fluoride/glycerol conversion coating solution on aluminium alloy, AA6061. From gravimetric studies, the nano-coatings formed on aluminium alloy by immersion procedures developed rapidly at a rate which decreased with time of treatment and was about 5 gm-2after a period of three minutes. The morphology of the coating from scanning electron microscopic (SEM) examinations revealed randomly shaped coating materials with mud cracking patterns, characteristics of dried out coatings derived from gel-like materials. Analyses of the coating with the energy dispersive analysis of X-ray spectroscopy (EDS) attachment in the SEM revealed the composition as compounds of aluminium, oxygen and manganese, probably hydrated. The corrosion resistance of the coating out-performed ‘bare’ aluminium alloy specimens exposed to both natural and 3.5% sodium chloride solution environments. The coating improved the paint adhesion characteristics of the substrate aluminium alloy. Macro and micro features developed on the substrate aluminium are anchor points which improved the adhesion of subsequently applied lacquer.