Influence of the chemical composition and of the hardened state of four cast Ni-based and Co-based cast alloys on their behaviour in corrosion by an artificial saliva. Part 1: Case of the nickel alloy studied using stationary electrochemical techniques and EIS

摘要

Nickel-based alloys containing molybdenum and chromium for mechanical and chemical resistance purpose represent a cheap alternative to noble metals (e.g. Au, Pt or Pd) and their alloys. Their use in the buccal milieu in which contact with aerated saliva is possible, as in the case of metallic frameworks emerging a little from the artificial teeth, corrosion is possible with as consequences the release of Ni~(2+) ions to which the patient may be allergic. In this work it was wished to investigate the electrochemical behaviour of simplified versions of a nickel-based dental alloy in a solution featuring among the ones usually used for simulating saliva, in order to explore the possible effects of the presence of silicon and of an eventual plastic deformation, issued from stress applied during mastication, on the corrosion rate. Two alloys, a ternary NiMoCr one and a quaternary NiMoCrSi one, were elaborated by casting and mounted as electrodes without or with preliminary hardening in compression, before being subjected to EIS and cyclic polarization runs in a three-electrode cell heated at human body temperature. Both alloys demonstrate high resistance against corrosion, with I_(corr) values significantly equal to or lower than 1 (iA/cm2. The presence of silicon as well a preliminary plastic deformation seems leading to a slight deterioration of the corrosion behaviour.