A TECHNIQUE FOR MEASUREMENT OF POROSITY IN PROTECTIVE COATINGS

A technique for measuring open porosity in protective coatings compose d mainly of refractory compounds has been developed. The technique inc ludes examination of electrochemical characteristics of the substrate and coating materials which results in estimation of the parameters co rresponding to the passivation of the coating and active dissolution o f the substrate. The coating porosity is defined then as the ratio of the anodic current of the substrate with and without the coating by us e of either potentiodynamic or chrono-amperometric procedures. The por osity measurement of some conventional CVD and PVD coatings was carrie d out using the technique.