LOW-NOBLE METAL-ALLOYS - INVITRO CORROSION EVALUATION

The electrochemical behaviour and the resistance to corrosion and tarn ishing of seven commercial low-noble metal alloys were investigated, i n artificial saliva at two different pH values (3 and 6.7) and in 2% N a2S solution. The alloys were tested as-received and after a hardening treatment suggested by the manufacturers: ageing 15 min in a temperat ure range between 360 and 450-degrees-C. Scanning electron microscopy (SEM) examination of the alloys evidenced some slight microstructural modifications. The electrochemical characterization was performed by m eans of anodic polarization curves. Alloys with noble metal content > 30% show a good electrochemical behaviour and a satisfactory corrosion resistance against tarnishing, and the hardening treatment had no inf luence on the corrosion resistance.