Sub critical crack growth in hydrogen assisted cracking of cold drawn eutectoid steel E. Proverbio a, * , P. Longo b a University of Messina, Department Industrial Chemistry and Materials Engineering, S. Agata di Messina, Contrada di Dio, 98166 Messina, Italy b Sidercem srl, Via Agnelli 22, Misterbianco, Italy Received 1 July 2005; accepted 1 December 2006 Available online 24 December 2006 Abstract The fracture behaviour of eutectoid cold drawn steel wires under constant load in hydrogen charged condition was evaluated. Hydrogen charging was obtained by dipping steel wires in ammo- nium thiocyanate solution. Sub-critical crack growth was monitored by means of Acoustic emission (AE) technique. Fractographic analysis revealed a mixed mode crack propagation (mode I and mode II) characterized by a multi-terrace appearance of the surface fracture. A modification of the macroscopic mechanical behaviour of the steel was also evidenced by micro hardness measurements. A simplified stress-assisted hydrogen diffusion model was used to interpret experimental observa- tions and to estimate a theoretical crack propagation rate. Such a value was in accordance with that obtained from the analysis of AE data. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: A. Low alloy steel; B. Modelling studies; B. SEM; C. Hydrogen embrittlement 1. Introduction Cold drawn carbon steels are massively used in prestressed and post-tensioned concrete structures. Development of corrosion attacks, due to diffusion of contaminant agents (pri- marily CO 2 and Cl  ) in protective concrete cover or application of cathodic protection 0010-938X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2006.12.005 * Corresponding author. Tel.: +39 090 3977243; fax: +39 090 3977471. E-mail address: proverbi@ingegneria.unime.it (E. Proverbio). Corrosion Science 49 (2007) 2421–2435 www.elsevier.com/locate/corsci