CORROSION SCIENCE SECTION CORROSION—Vol. 67, No. 7 075001-1 Submitted for publication July 26, 2010; in revised form, January 25, 2011. ‡ Corresponding author. E-mail: toribio@usal.es. * Department of Materials Engineering, University of Salamanca, EPS, Campus Viriato, Avda. Requejo, 33, 49022 Zamora, Spain. ** Department of Mechanical Engineering, University of Salamanca, ETSII, Avda. Fernando Ballesteros 2, 37700 Béjar, Spain. *** Department of Mechanical Engineering, University of Salamanca, EPS, Campus Viriato, Avda. Requejo, 33, 49022 Zamora, Spain. Hydrogen Degradation of Cold-Drawn Wires: A Numerical Analysis of Drawing-Induced Residual Stresses and Strains J. Toribio, ‡, * M. Lorenzo,** D. Vergara,*** and V. Kharin* ABSTRACT Hydrogen degradation represents a problem of major tech- nological concern in the structural integrity of prestressed concrete structures in which cold-drawn wires are the main structural component and can suffer the deleterious effect of hydrogen, with the subsequent risk of catastrophic fail- ure. This paper presents an innovative numerical analysis of hydrogen degradation of cold-drawn prestressing steel wires, focused on the two relevant variables influencing the phenom- enon of hydrogen transport by diffusion in the metal: residual stresses generated by manufacture and plastic strains after cold work. To achieve this goal, two real (industrial) drawing processes are analyzed with two main differences, namely, the reduction of cross-sectional area performed at the first drawing stage and the number of drawing steps used in the whole process. Generated results prove the importance of an adequate design of the cold-drawing process with regard to the residual stress-and-strain field and its relevant role in hydrogen diffusion in the wires, as well as its possible conse- quences for hydrogen degradation and, thus, for catastrophic failure. KEY WORDS: cold-drawn wires, hydrogen embrittlement modeling, residual stresses and strains INTRODUCTION Cold-drawn pearlitic steel wires are used widely for prestressing civil engineering concrete structures. During their habitually decades-long service, the wires usually are subjected to influences of harsh environments, e.g., atmospheric humidity. As a con- sequence, they become susceptible to damage and fracture as a result of deleterious synergic effect of applied load and environment, which is commonly referred to as stress corrosion cracking (SCC) 1 that has the hydrogen-assisted fracture (HAF) as one of its frequently met forms. 2-3 Then, analysis, assessment, and control of HAF of prestressing wires is the key issue for structural integrity in civil engineering, and the relevance of hydrogen damage for structural dete- rioration is stated profusely in scientific literature. 4-6 To fit prestressing steels for a purpose, cold-draw- ing is the key issue in wire manufacturing that ren- ders a substantial increase in their strength, 7 so that the wires can satisfy the requirements established for highly resistant structural elements. In addition, the drawing process introduces residual stresses in wires whose supreme importance for wire performance has been well recognized. 8-12 Residual stresses, which are generated by particular drawing procedures and even- tually modified by some posterior heat or surface treatment, 12 bear, per se, a great deal of responsibility for structural short-term strength under applied trac- tion in service. Moreover, with regard to the deleteri- ous environmental effects on the wires’ strength and life, particular importance of residual stress states for ISSN 0010-9312 (print), 1938-159X (online) 11/000081/$5.00+$0.50/0 © 2011, NACE International