Discussion on “Failure mechanisms of high strength steels in bicarbonate solutions under anodic polarization” by E. Proverbio and P. Longo

Proverbio and Longo have reported some results on the stress corrosion cracking behaviour of cold drawn pearlitic steels in a sodium bicarbonate aqueous solution. On the basis of fractographic observations, mechanical analysis and the application of the surface mobility mechanism (SMM) they conclude that cracks are generated by anodic dissolution at localized ruptures of the passive film, with hydrogen playing an essential role in their propagation. A close examination of the paper shows a misinterpretation of the fractographical evidence, and an inappropriate mechanical reasoning as well as an incorrect application of the SMM. As a consequence, the conclusions are not supported by the results.