Influence of permanganate reduction on CaCO3 crystals' growth on a rotating metal surface

Abstract

CaCO3 growth on a stainless steel rotating electrode surface has been carried out in optimised conditions. Without permanganate ions in the solution, the formed scale appears compact and sticky as it is confirmed by microscopic observations and the low residual current density observed at cathodic polarisations.In this work we were interested by the behaviour of permanganate on CaCO3 growth because it is generally considered as a corrosion inhibitor. Permanganate ions injected in the solution are readily reduced at cathodic potentials, provided that the ions reach the surface of the polarised electrode. Permanganate reduction leads, through several steps, to the formation of MnO2. This semi-conductor specie has the particularity to be solid and develops on the metal surface. CaCO3 growth on a surface electrode covered by MnO2 remains possible. But the deposit formed appears to be porous and much less adherent than without manganese species. Our observations obtained at 25°C have been verified at higher temperatures.