Investigation of the passive layer on a solid-state sintered silicon carbide ceramic formed in sulfuric acid

The presented work considers the electrochemical behavior of SSiC. The passive behavior and structure of the near surface region are characterized by means of cyclovoltammetry, electrochemical impedance spectroscopy, and XPS. Electrochemical measurements and surface analysis reveal the formation of a near-surface region which can be described as amorphous non-stoichiometric SiOx, SiOxCy. After polarization at 1500 mVSCE the thickness of this oxidized region is in the range of 4-5 nanometers. The formation reaction of SiC to SiOx is explained by a 4-electron mechanism under the formation of carbon. Additionally, anodic oxygen evolution must be assumed to 20%-30% efficiency at this potential.