IMPEDANCE SPECTROSCOPY OF OXIDE AND CONVERSION FILMS ON THE SURFACE OF ALUMINUM-ALLOYS

Impedance spectroscopy was used for measuring the electrical propertie s of two types of surface film on an aluminum alloy. The oxide film wa s formed by machining the alloy at free access of air using a diamond tool and a special cooling liquid. The chromate-phosphate one was prod uced by chemical conversion. Models of the structural features of the films are suggested. The models are in agreement with results of addit ional experiments, in which electrical characteristics of the films ar e modified by means of changing the conductivity of the electrochemica l system as well as thermal treatment of the film.