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Liquid-phase sintered silicon carbide (LPS-SiC) is silicon carbide ceramic which contains sintering additives forming a liquid phase during sintering. These additives segregate in the grain boundary phase during cooling. The usually used Al2O3 dissolves partially in the SiC-grains and therefore changing the conductivity of the SiC (core rim structure). This study is focused on the electrochemical properties of LPS-SiC with yttria and alumina as sintering additives. Electrochemical corrosion behaviour of LPS-SiC has been determined by linear and cyclic voltammetry in acidic and alkaline solution. The effect of anodic oxidation on the material has been monitored by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) as well as by atomic force microscopy (AFM). The core-rim structure of the investigated materials plays a decisive role in the vulnerability towards corrosion. If oxidative attack was found to occur under anodic polarization, it happened preferentially in the rim region of the SiC-grains, while the core of the SiC-grains remained basically unaffected

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Recently, SiC‐based ceramics have been found to exhibit corrosion damage patterns, which can only be explained by electrochemical processes. Therefore, the current work focusses on the electrochemical test procedures to determine the corrosion behaviour of solid state sintered silicon carbide (SSiC) ceramics in acidic and alkaline media. The corrosion current densities have been determined from linear voltammetric scans. At anodic polarization potentials, electrochemically induced etching patterns were observed in alkaline solution. The formation of pores and crevices during electrochemical oxidation in acidic solution could be monitored by field emission scanning electron microscopy (FESEM) in addition to transmission electron microscopy (TEM). Impedance spectra measured after anodic polarization could be described by the assumption of a pore model equivalent circuit.

In order to understand the relationships which exist between the microstructures and mechanical properties of ceramic materials and to clarify their respective mechanisms of corrosion, a detailed picture of their microstructures is of particular importance. The examination of such structures using field emission scanning electron microscopy in combination with EDX analysis as well as the FIB technique are demonstrated on polished and electrochemically corroded LPS (liquid phase sintered SiC) and SSiC materials. The possibilities for revealing the diffusion zones in semi-conducting SiC grains are presented. These methods also help to explain the core-shell structures caused by electrochemical corrosion.