On structure and oxidation behaviour of non-stoichiometric amorphous aluminium phosphate coating

ABSTRACT

The purpose of this study was to investigate the structure and oxidation behaviour of non-stoichiometric aluminium phosphate coating. Phase composition analysis was performed by X-ray diffractometer (XRD). Fourier transform infrared (FTIR) was used for molecular spectroscopy. The micro-structural studies were investigated by TEM. AISI 304 stainless steel substrates were dip coated in the aluminium phosphate solution to evaluate the cyclic oxidation behaviour. The oxidised samples were characterised by SEM/EDS and XRD techniques. The XRD patterns and TEM images confirmed the amorphous structure of as-synthesised aluminium phosphate. Based on the FTIR result, the non-stoichiometric amorphous aluminium phosphate owned Al−O−Al bonding besides Al−O−P. Weight change measurements after 100 h oxidation at 1100°C revealed that the range of the weight gain of the bare substrate was 30 times higher than that of the coated one.

KEYWORDS:

• Aluminium phosphate
• amorphous coating
• sol-gel
• oxidation resistance

Acknowledgement

The authors greatly appreciate the generous support of Department of Chemistry, Materials and Chemical Engineering, Polytechnic University of Milan, Italy and in particular, Professor Massimiliano Bestetti on this research.

Disclosure statement

No potential conflict of interest was reported by the authors.