Effects of some parameters on corrosion behaviour of plasma-sprayed coatings

The corrosion behaviour of ceramics and cermet coatings on AISI 304L steel substrates was investigated in several aqueous solutions. Plasma spray process was employed on substrates with the deposition of ceramic and cermet powders such as Al₂O₃, Al₂O₃+TiO₂ and Cr₂C₃+ NiCr. The porosity of coatings was measured by an electrochemical technique. Potentiodynamic polarization measurements and corrosion tests were employed to determine the corrosion behaviour of plasma-sprayed coatings. The micro structures of powders and coatings were investigated by means of an optical microscope, SEM, and X-ray diffractometry. The obtained results show that the protection against corrosion depends strongly on the porosity, thickness, surface roughness of the coatings, corrosion media and rotating speed of samples.