Delafosse, D, B Bayle, and C Bosch. 2007. “The Roles of Crack-Tip Plasticity , Anodic Dissolution and Hydrogen in SCC of Mild and C-Mn Steels.” In Environment-Induced Cracking of Metals (EICM) - Volume 2: Prediction, Industrial Developments and Evaluation, edited by S Shipilov, R Jones, J M Olive, and R Rebak, 267–78. Banff, Alberta, Canada: Elsevier. doi:10.1016/B978-008044635-6.50064-9. 1 of 10 The role of crack-tip plasticity, anodic dissolution and hydrogen on the SCC of C-Mn and low-alloy steels D. Delafosse, B. Bayle, C. Bosch SMS division, UMR CNRS 5146, Ecole Nationale Supérieure des Mines,158 cours Fauriel, 42023 Saint - Etienne, France Abstract We present results from two different studies on the SCC and hydrogen-induced SCC of structural steels. The various microstructure / environment / mechanical loading combinations encountered allow to highlight the respective weight of anodic dissolution, hydrogen effects and crack tip plasticity on the damage processes. The case of mild steels in methanolic solutions is first presented. It is shown that micro-galvanic coupling between carbides and the ferritic matrix prevails in the crack initiation mechanism, and remains an important parameter in the propagation mechanism. We then report on a study of the near neutral pH SCC of two pipeline steels in simulated ground water, where hydrogen effects strongly influence the SCC resistance in the presence of MnS precipitates. The specific role of crack-tip plasticity is highlighted by the specific use of micro-notched tensile specimens Keywords: A - low alloy steel ; A - mild steel ; C - stress corrosion ; C - cathodic protection ; C - effects of strain 1. Introduction Environmental sensitive fracture of carbon or micro-alloyed steels occurs in a variety of environments. In many instances, both anodic dissolution and hydrogen effects are involved and interact with crack-tip plasticity. From an experimental point of view, separating these contributions is not straightforward, especially in when the respective weight of these contributions vary during the process of crack propagation. In this paper we present results from two different studies recently conducted. The various microstructure / environment / mechanical loading combinations allow to highlight the respective weight of anodic dissolution, hydrogen effects and crack tip