Abstract
The effets of Cr contents on the corrosion resistance of Ni-Cr binary alloys and Mn, Si, Cu or Mo contents of Ni-Cr binary alloys were investigated. The alloys were prepared with the composition of Cr ranging from 0 to 39.8 wt%. Additions were made to Ni-5% Cr and Ni-20% Cr alloys as follows:Mn 0.5, 2.0 wt%, Si 2.0, 5.0, 10.0 wt%, Cu 2.0, 5.0, 10.0 wt%, Mo 2.0, 5.0, 10.0 wt%. The corrosion resistance was assessed by the release of Ni in Ringer's solution at 37℃ and 1% lactic acid at 37℃, and by electrochemical corrosion behavior in Ringer's solution.
The results are summarized as follows.
Ni-Cr binary alloys were classified into three types of Cr ranging from 0 to 5.5 wt%, Cr from 10.8 to 21.0 wt% and Cr from 26.3 to 39.8 wt% according to the release of Ni in Ringer's solution. It is necessary to keep the Cr contents to a minimum of 10.8 wt% for released Ni and rest potential values in Ringer's solution and 15.7 wt% for restraint of released Ni in 1% lactic acid. Alloys containing Mn exhibited the decline in the corrosion resistance. Si addition to Ni-5% Cr alloy had the effect of increasing the corrosion resistance and the alloy with Si 4.6 wt% showed the best corrosion resistance. Alloys containing Cu exhibited good corrosion resistance to the release of Ni and the rest potential value, but not in the anodic polalization curve. Alloys containing Mo exhibited good corrosion resistance and the optimum additive amount of Mo was affected by Cr content. In the case of the alloys with Cr 5.5 and 21.0 wt% contents, the optimum additive amounts of Mo were 1.7 and 7.1 wt%, respectively.
