Long-term corrosion behavior of HVOF sprayed Cr3C2–NiCr coatings in sulfide-containing 3.5 wt.% NaCl solution

Abstract

In this work, Cr3C2–NiCr coatings were fabricated by high-velocity oxygen-fuel (HVOF) spraying. Under the help of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and optical microscope (OM), the phase compositions and microstructure of the coatings were characterized. The long-term corrosion behavior of HVOF sprayed Cr3C2–NiCr coating (HC) and Q345 steel was probed in 3.5 wt.% NaCl solution (S1) and 3.5 wt.% NaCl solution containing 20 ppm Na2S (S2). With the extension of immersion time, the corrosion rate of HC in different solutions showed an overall trend of increasing first and then decreasing. The corrosion rate of Q345 steel in both of the solutions showed a growing trend, while the trend in the sulfide-containing solution was even sharper. The corrosion rates of HC in S1 and S2 were both lower than those of Q345 steels, especially in S2. Owing to the generation of the dense protective film on the HC surface as well as the accumulation of corrosion products, after 70 d of immersion, HC exhibited better corrosion resistance in S2 than that in S1.