Improving corrosion resistance of nickel-aluminum bronzes by surface modification with chromium ion implantation

As-cast nickel-aluminum bronze is prone to suffering selective phase corrosion in marine environments. To solve this problem, chromium was introduced via ion implantation to modify its surface microstructure, which was characterized by high-resolution transmission electron microscopy and auger electron spectroscopy. The corrosion behavior was studied by electrochemical measurements and salt spray test. It was found that the inherent selective phase corrosion in as-cast NAB was inhibited effectively when the implantation fluence was 5 x 10(17) ions/cm(2). The improved corrosion resistance after ion implantation was believed to stem from the rapid formation of a more protective film containing chromium oxides and hydroxides.