Research Paper
Effect of Ta Addition on Crevice Corrosion Resistance for Ni Based Corrosion Resistant Alloys
2010 Volume 59 Issue 6 Pages 222-227
Details
2010 Volume 59 Issue 6 Pages 222-227
The effects of small amount of tantalum addition to a Ni-Cr-Mo alloy on crevice corrosion resistance in 25% NaCl at 107°C was investigated quantitatively by measuring the repassivation potentials for corrosion crevice (ER,CREV). Upon the results, tantalum was revealed to shift the repassivation potentials to the noble direction and the effect was much more than the chromium or molybdenum. For the tantalum free alloys, the crevice corrosion resistance was found to correlate closely with the Pitting Resistance Evaluivalent number (PRE=[%Cr]+3.3([%Mo]+0.5[%W])), however, the tantalum containing alloys were against the correlation. Consequently, PRE(Ta)(=[%Cr]+3.3([%Mo]+0.5[%W])+7.7[%Ta]) was induced by adding a term of [%Ta] to the PRE equation. With this PRE(Ta), the crevice corrosion resistance for the tantalum containing alloys can be estimated.
