THE SUSCEPTIBILITY TO SURFACE CORROSION IN ACIDIC FLUORIDE MEDIA - A COMPARISON OF DIAMOND, HOPG, AND GLOSSY CARBON ELECTRODES

The chemical inertness and corrosion resistance of a boron-doped diamo nd thin film electrode, grown by chemical vapor deposition (CVD), have been studied during potential cycling (PC) for 2 h in a solution of 1 .OM HNO3 + O.1 NaF at 50 degrees C. Similar experiments were performed on highly ordered pyrolytic graphite (HOPG) and glassy carbon (GC), f or comparison. The physicochemical properties of the electrode surface were characterized before and after PC by cyclic voltammetry, optical and scanning electron microscopy, Raman spectroscopy, and ac impedanc e spectroscopy. The results indicated that the diamond electrode posse sses a superior degree of chemical inertness and corrosion resistance, has no microstructural damage nor was surface oxidation observed afte r PC. HOPG and GC surfaces, on the other hand, exhibited severe corros ion in the form of surface cavitation, pitting, and oxidation. The rel ative degree of microstructural damage and surface oxidation increased in the order of diamond << HOPG < GC. This work represents some of th e initial efforts at systematically characterizing how the physical, c hemical, and electronic properties of conductive diamond thin films ar e affected during exposure to electrochemical conditions (i.e., solven t, electrolyte, and applied potential).