EVALUATION OF POROSITY OF HARD COATINGS BY CORROSION ELECTROCHEMSTRY
腐蚀电化学方法评价硬质涂层孔隙率

The principle and the measurement for the porosity of hard coatings on the metal surfaces were summarized. The transmission line model for a single one - dimensional pore and finite diffusion model based on electrochemical impedance theory and the porous coating model based on anodic polarization theory were provided. The porosity measured by the transmission line model was obtained through the relation of polarization resistances of coating-substrate system and coating and substrate. Using the function between the porosity and the diffusion coefficient and frequency in the diffusion impedance, the finite diffusion model evaluated the porosity. For the porous coating model, the porosity was determined by the parameters of the anodic current densities, polarization resistances, corrosion potentials and coulometric charges between the coated and the substrate, respectively. Compared with the porosity determined from measurements for hard coatings deposited under different processing conditions, the range of the porosity was 0. 001% - 50 %. The measurement precision was above 80 %.