The effect of immersion time on corrosion performance of the Al 2 O 3 -40TiO 2 and WC-10Co-4Cr coatings in 3.5 wt.% NaCl solution

Abstract The Al 2 O 3 -40TiO 2 and WC-10Co-4Cr coatings were fabricated by air plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying, respectively. The microstructure, corrosion resistance and eroded surface of the coatings were characterized. The effect of immersion time on corrosion behavior of the coatings in NaCl solution was investigated. Contrasting to the Al 2 O 3 -40TiO 2 coating, the corrosion resistance of the WC-10Co-4Cr coating was still higher before 42 days of immersion. However, the corrosion resistance of the Al 2 O 3 -40TiO 2 coating was higher than that of the WC-10Co-4Cr coating, when the immersion time reached 70 days. With the increase of immersion time, the galvanic corrosion accelerated the formation of pits and craters as well as decreased the corrosion resistance of the WC-10Co-4Cr coating. Meanwhile, corrosion products accumulated in the pits and promoted the stress cracking in the Al 2 O 3 -40TiO 2 coating, which caused the fact that the corrosion resistance of the Al 2 O 3 -40TiO 2 coating increased firstly and then decreased.