Abstract
Corrosion resistance to crevice corrosion attack of welds made with various Ni-Cr-Mo(-Ta) alloy fillers connected to Ni-based alloy plates in a hot concentrated NaCl solution was investigated using the technique of measuring repassivation potentials for crevice corrosion (ER,CREV). The ER,CREV of the test electrode with a weld could be regard as it of the weld. Under this condition it was made clear that the dendrite core where was the alloy element depleted region determined the corrosion resistance to crevice corrosion attack of the weld to be degraded it. ER,CREV of weld has linear relationship to Pitting Resistance Equivalent with tantalum (PRE(Ta)=[%Cr]+3.3([%Mo]+0.5 [%W])+7.7 [%Ta]) which is calculated from dendrite core composition. The line consistents with the relationship between ER,CREV of base metal and PRE(Ta) which is calculated from its chemical compotion. Under more severe conditions for crevice corrosion such as higher temperature, the ER,CREV of alloy 22 showed the same value with it of the weld made with the filler having the same composition of the base metal. It was suggested that the depnendance of the corrosion resistance to crevice corrosion attack of the weld changed into its average chemical composition from the dendrite core composition.
