Electrochemical impedance spectroscopy of HVOF-sprayed NiTi intermetallic coatings deposited on AISI 1045 steel

NiTi intermetallic coatings were sprayed on AISI 1045 steel substrate by using high velocity oxygen-fuel (HVOF) process. Polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to study corrosion behavior of the coatings in 3.5% NaCl solution. Polarization tests indicated that the corrosion current densities of the HVOF coatings are comparable to those of NiTi alloys reported in the literature. On the other hand, EIS measurements showed that although the solution penetrates through the coating defects and causes to corrosion of the substrate, but, the corrosion performance of the coatings improves at long times due to the plugging of the defects by corrosion products which hinders higher attack of the substrate.

Research highlights▶ Penetration of solution through the coating defects and corrosion of the substrate. ▶ Improvement in corrosion behavior of HVOF NiTi coatings at long times due to the plugging of the defects by corrosion products.