Comparative Study on the Corrosion Performance of APS-, HVOF-, and HVAF-Sprayed NiCr and NiCrBSi Coatings in NaCl Solutions

Corrosion performance of NiCr and NiCrBSi coatings produced by APS, HVOF, and HVAF was studied by electrochemical measurements and immersion tests in 0.5 and 3.5 wt.% NaCl solutions. In the electrochemical measurements, the NiCr coatings performed better than the NiCrBSi coatings. The effect of the coating process on the corrosion resistance of the material was significantly lower than that of the selected materials, NiCr or NiCrBSi. All the coatings showed a tendency to passivate but suffered from localized corrosion. During immersion exposure for ten weeks, localized corrosion appeared at heterogeneous areas of the coatings, including voids, defects, or powder particles that had not melted during the spraying process.