Passivation Degradation of Alloy 800 in Boiling Solution Containing Thiosulphate

The effect of boiling bubbles on the passivation degradation of Alloy 800 in thiosulphate-containing aqueous electrolyte was experimentally investigated using corrosion potential, anodic polarization, combined with Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). The results showed that the boiling bubbles decreased the pitting potential by enhancing the mass transport. The specimen immersed in boiling electrolyte have a thicker anodic film and a greater amount of sulfur incorporation into the passive layer compared with the experiments at 99 °C. Moreover, a higher ratio of low valance sulfur species was detected on the specimen in boiling test electrolyte, indicating that the boiling bubbles reduced the corrosion resistance of Alloy 800.

108