Comparative study on stability of boron doped diamond coated titanium and niobium electrodes

The service life of boron doped diamond (BDD) coated electrodes is closely related to the substrate material and preparation process of the BDD coatings. In this paper, the failure process of BDD coated titanium (Ti/BDD) and niobium (Nb/BDD) electrodes prepared by arc plasma chemical vapor deposition method was comparatively studied by accelerated life test. The results showed that the main failure mechanism of the two types of electrodes is delamination of the BDD coatings, accompanied by coatings' corrosion. The delamination of BDD coatings from both the substrates showed an incubation period, with the Ti/BDD electrode having a much shorter incubation period and a higher coating delamination rate than its Nb/BDD counterpart. By comparing growth process of diamond coatings and corrosion behavior of carbides formed on both substrates, it is found that on a Ti substrate, diamond coating is more liable to incorporate pore like defects, and carbide layer formed beneath the diamond coating is more susceptible to corrosion in electrolysis solution. It is believed that these two factors would be responsible for short service life for Ti/BDD electrodes as compared with that for Nb/BDD electrodes.