Corrosion of Simple Cobalt-Chromium Alloys, Bases of Real Dental Alloys Devoted to Prosthetic Dentistry, in a NaCl Solution Simulating Human Saliva Specified by Stationary Electrochemical Techniques and EIS

Abstract

Cobalt-based alloys containing chromium in quantity high enough represent a cheap alternative to dental alloys involving high quantities of noble metals (Au, Pt, Pd…). However, their general corrosion behaviour is not necessarily excellent and their use in the buccal milieu, which supposes contact with saliva, may lead to the release of ions to which the patient may be particularly sensible: allergic reaction, disease due to cobalt ions, associated troubles… In this work it was wished to investigate the electrochemical behaviour of extremely simplified versions of commercial cobalt-based dental alloys in a solution featuring among the ones usually used for simulating saliva. The aim was to explore the possible effects on the corrosion rate of the chromium content and of an eventual plastic deformation issued from fabrication or from mastication. Two binary alloys, Co-15wt.%Cr and Co-30Cwt.%Cr, mounted as electrodes, without or with preliminary hardening in compression, were subjected to EIS and cyclic polarization runs in a threeelectrode cell heated at the human body temperature. Both alloys demonstrated high resistance against corrosion, with I_corr values significantly lower than 1 μA/cm², without real effect of the chromium content (15wt.% seems enough) or of preliminary plastic deformation.