ELECTROCHEMICAL EVALUATION OF HARD IBAD COATINGS USING A SCANNING ELECTROCHEMICAL MICROELECTRODE

The quality of thin surface coatings for wear and corrosion protection is significantly influenced by pores and film defects (voids, micro c racks, coated impurities), which can be formed in the processing stage . These defects are the initiation sites, and are responsible for mech anical and chemical failure of the film. There are processes of oxidat ion and corrosion of the substrate especially at the site of pores. To meet the requirements of protection the processing stage has to be op timized by minimizing flaws and pores. Suitable testing methods are ne cessary for early diagnosis and recognition of chemical and mechanical degradation of the film or dissolution of the substrate, respectively . The investigations, presented in this paper, were carried out with T IN layers and TiO2-->TiN multilayers on steel (Ck45) produced by ion b eam assisted deposition. The thickness of the film was between 1 and 1 .5 mu m In order to obtain a high local resolution of the corrosion ph enomena occurring on the surface, electrochemical equipment with a goo d lateral resolution through a microelectrode of 10 mu m was developed . The contribution shows the evaluations of the films and defects in a queous solution. The scanning electrochemical results are represented as topographical three-dimensional images of the electrochemical surfa ce reactivity. (C) 1998 Elsevier Science S.A.