Corrosion of graphite in industrial phosphoric acid

The electrochemical corrosion of graphite in industrial phosphoric acid solutions was studied using polarisation curves analysis, cyclic voltammetry, MEB–EDS and secondary ions mass spectroscopy (SIMS). The polarisation curves indicated that graphite has a passive behaviour and the increase of temperature induces an increase of the corrosion rate and the passive current density. The cyclic voltammetry analysis was performed to verify the surface phenomenon of graphite surface and confirmed the role of adsorption oxygen in material corrosion. Spectroscopic analysis (EDS and SIMS) showed that the majority of industrial phosphoric acid impurities were present in the graphite composition indicating that metallic oxides are not the only components of this layer. The presence of these impurities on the graphite induces an increase of corrosion by swelling, exfoliation and cracking.