The Influence of Ni Incorporation on the Porosity and Corrosion Resistance of CrBN Coatings in Seawater

To improve the corrosion resistance of CrBN coatings in seawater, the anti-corrosion element Ni at different concentrations was incorporated. After Ni incorporation, CrNiBN coatings showed compact morphology, and the surface porosity decreased from 16.8 % to 7.7 %. As a consequence, all of CrNiBN coatings presented stronger corrosion resistance than CrBN coating. Moreover, with the increase of Ni concentration from 4.35 at% to 7.28 at%, the corrosion resistance of CrNiBN coatings became good first owing to the combination effects of compact morphology and high self-corrosion potential. However, the more Ni doping of 19.62 at% would decrease self-corrosion potential and trigger oxidation so as to weaken the corrosion resistance of CrNiBN coatings. Among all of CrNiBN coatings, the CrNiBN-240 coating with 7.28 at% Ni presented the highest charge transfer resistance Rct of 1.965×104 Ω·cm² and the highest polarization resistance Rp of 74.9 kΩ·cm².