Sputter-grown hierarchical nitride (TiN & h-BN) coatings on BN nanoplates reinforced Al7079 alloy with improved corrosion resistance

Abstract

A boron nitride nanoplates (BNNPs) reinforced aluminium alloy (Al7079) based ex-situ metal matrix (MM) nano-composite was successfully developed via mechanical stir casting process. This MM nano-composite shows better wetting and anti-corrosion properties in comparision of bare Al7079 alloy. To further enhance the aforementioned properties, two dissimilar hard coatings (TiN & h-BN) with hierarchal rough surfaces were employed on the BNNPs functionalized MM composite surface via a single-step PVD technique, which provide a tough barrier with non-wetting surface to prevent the base material from corrosion attack. The addition of these layers led to a significant change in physical, chemical, mechanical and anti-corrosion properties. The results also revealed the hydrophobicity of developed coatings with optical contact angle meter of TiNNCs and h-BNNPs surfaces ~102.1° and 141.6°, respectively. The collective results obtained from electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests revealed the one order higher corrosion resistance of h-BN coated sample than TiN coated sample under saline media (3.5 wt%). This coating may be a promising candidate in various applications, where the protection of materials against corrosion is necessary. • Development of BN nanoplates reinforced aluminum alloy (Al-7079) metal matrix by mechanical stir casting. • The MM nano-composite shows better wetting and anti-corrosion properties as compare to base Al7079 alloy. • TiNNCs and h-BNNPs were employed on the BNNPs-Al7079 composite surface via a single-step PVD technique. • Better hydrophobicity and high corrosion resistance shown by BNNPs coated sample compared to TiNNCs coated sample.