Ultrasound−assisted sealing with different sealants for enhanced corrosion protection of HVOF−sprayed WC−Cr3C2−Ni/CNTs coating in 3.5 wt% NaCl solution

High−velocity oxygen−fuel (HVOF) sprayed WC−Cr3C2−Ni/CNTs coatings were prepared on 430 stainless steel, and then were sealed with sol–gel aluminum phosphate (inorganic sealant) and silicone resin (organic sealant) by ultrasound−assisted sealing technique. The morphologies, compositions and corrosion performance in 3.5 wt% NaCl solution of the coatings before and after sealing were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and electrochemical workstation, respectively. The wettability of different sealants and coating was investigated by contact angle measurement. The corrosion current densities of the sealed coatings were reduced, and the resistivity was increased by a factor of about two (inorganic sealant) and four (organic sealant), which resulted in improved corrosion resistances. The contact angle between organic sealant and coating was lower than that of inorganic sealant. Ultrasonic sealing improved the combination of the sealants and the coating pores, and the effect of organic sealant on improving corrosion resistance was more superior.