Abstract
The effects of Cu content on the corrosion resistance of Ni-Cr alloys were investigated.Cu was added in 5wt% increments to 30wt% in Ni-15Cr alloys.The alloys were evaluated in as-cast condition using Ringer's solution.By applying the square wave current method, the polarization resistance was measured for 50 days, along with corrosion potential.The average corrosion rate was calculated from the weight loss of test pieces.The corrosion potential became noble and polarization resistance increased with addition of Cu.The results indicated that the tendency for Ni-Cr alloys to passivate was enhanced by the addition of Cu.X-ray microanalyses on tested specimens revealed the presence of segregations and Cu rich regions were corrosion resistant.It was also demonstrated by atomic absorption spectrophotometry that Ni was dissolved into Ringer's solution whereas the amounts of Cr and Cu ions were small.The average polarization conductance values during the test period were related to the real corrosion rate as:icorr =K・Ycorr The constant K value for Ni-Cr alloys determined in Ringer's solution at 37℃ was 26mV.
