ELECTRON-OPTICAL AND AUGER ELECTRON SPECTROSCOPY STUDIES OF A ZIRCONIUM CONVERSION COATING ON ALUMINIUM

Adediran, A.A and Oki, Makanjuola and Akintola, Sarah Abidemi and OGUNSEMI, B.T. and Akinlabi, Esther Titilayo (2019) ELECTRON-OPTICAL AND AUGER ELECTRON SPECTROSCOPY STUDIES OF A ZIRCONIUM CONVERSION COATING ON ALUMINIUM. Materials and technology, 53 (2). pp. 183-188. ISSN 1580-2949

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Abstract

The techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultramicrotomy and energy dispersive X-ray analysis (EDX) were employed to examine conversion coatings on aluminium developed from a zirconium nitrate/fluoride solution. The coating developed slowly on a microscopic metal substrate with islands of zirconium-rich centres within the coating matrix. According to the TEM assessment, the coating thickness was 30 nm for specimens treated for 60 s and 50 nm for those treated for 900 s. The population of the zirconium-rich centers ranged from 2.8 × 1012 m–2 to 6 × 1012 m–2 over the treatment period. According to Auger-electron-spectroscopy in-depth analyses, the coating is composed of three diffused layers with an outer region of zirconium oxide followed by a layer of aluminium oxide/hydroxide and an inner layer at the metal/coating interface comprising compounds of aluminium and fluorides. The corrosion-resistance and paint-adhesion characteristics of the zirconium conversion coating are superior to those of bare aluminium.

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