Effects of environmental and metallurgical conditions on the passive and localized dissolution of Ti-0.15%Pd

The effects of chloride (Cl-) concentration, fluoride (F-) concentration, pH, temperature, and weldments on the corrosion behavior of Ti-O. 15%Pd (Ti Grade 7, UNS R52400) were examined, It was noted that, even at elevated temperatures (165degreesC), the passivity breakdown and repassivation potentials were well above 1 V vs saturated calomel electrode (SCE) in solutions containing 4 M Cl-. It was also observed that welded specimens exhibited lower breakdown and repassivation potentials than wrought specimens. Short-term anodic polarization tests revealed that Cl- concentration, pH, and applied potential had only a slight effect on the passive current density of Ti Grade 7. Fluoride additions to Cl- solutions resulted in the appearance of a pseudo-active/passive transition and a significant increase in the potential-independent anodic current density, which was several orders of magnitude greater than typical passive current densities. Also of note is the observation that, despite the use of creviced specimens, all corrosion attack took place on the boldly exposed surfaces of the specimens.