Corrosion resistance of NbN and Nb_xAl_yN coatings on stainless steel

ABSTRACT

Herein, the corrosion behaviour of coated 304 stainless steel in 3.5 wt-% NaCl solution was investigated. Thin films, composed of NbN and Nb_xAl_yN with different Al contents, were synthesized by magnetron sputtering. The microstructural investigation involved testing in energy-dispersive X-ray spectroscopy, scanning electron microscopy and grazing incidence X-ray diffraction, revealing films with a thickness of 165–200 nm composed of an NbN-δ cubic phase. Corrosion resistance was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy tests. According to the present results, in the proposed the experimental conditions, the addition of Al to NbN coatings is detrimental to the corrosion resistance of coated 304 stainless steel. The Nb_0.90Al_0.10N sample shows the lowest corrosion protection and the highest porosity among the studied samples.

KEYWORDS:

• Niobium nitride
• aluminium
• sputtering
• thin films
• corrosion

Acknowledgements

The authors would like to thank the Department of Materials Science and Engineering of the Federal University of Sergipe for the characterization tests and film depositions; the Department of Chemical Engineering of the Federal University of Minas Gerais for the corrosion measurements; and the Department of Materials Science and Engineering of the Federal University of Rio Grande do Norte for the FEG tests.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors would like to thank CAPES and undação de Apoio à Pesquisa e à Inocação Tecnológica do Estado de Sergipe (Fapitec/SE) for financial support.