Preface Modelling of reinforcement corrosion in concrete In 2000 a proposal was launched to install a new Task Group of Working Party 11 of the European Federation of Corrosion, EFC, on modelling of re- inforcement corrosion in concrete. Whereas the in- itiation stage of corrosion, i.e. chloride ingress and carbonation, has received considerable attention during recent years, actually little work has been performed on the propagation stage. The corrosion models currently available on propagation are es- sentially empirical and do not address the electro- chemical nature of the corrosion process. Although empirical models may provide a convenient tool for structural engineers to roughly predict service life of structures during the design stage, these models are considered less appropriate for evaluating specific practical cases. However, a useful application of electrochemical models requires a basic understand- ing of the underlying mechanisms. In this article in- formation on the activities of the EFC Task Group on Modelling of Reinforcement Corrosion will be highlighted. The Task Group, chaired by Michael Raupach and Joost Gulikers, organised 4 meetings (Aachen, Lux- embourg, Granada and Utrecht) to discuss its major activities in order to arrive at a common approach that could be applied on a number of situations of practical relevance. The working program included the elaboration of 3 practical case studies by researchers working in the field of reinforcement corrosion. A number of researchers contributed to the activities of the Task Group, notably Dubravka Bjegovic, Martin Brem, Michael Bruns, Gareth Glass, Joost Gulikers, Willy Peelen, Rob Polder. Michael Raupach, Elena Redaelli, Luca Bertolini, Alberto Sagu ¨e ´s and Ju ¨rgen Warkus. The aim of the EFC Working Group was to present an overview of the electrochemical corro- sion models currently in use and to suggest improve- ments for extended use in practice. In order to predict the electrochemical condition of steel reinforcement in concrete the polarisation behaviour, i.e. the current-potential relationship of the rebar has to be known. The electrode reactions usually considered to be of practical interest com- prise the oxidation of iron and the reduction of dis- solved oxygen. The kinetics of both reactions should therefore be incorporated in mathematical expres- sions adequately describing the polarisation behav- iour. In this respect a clear distinction has to be made between the characteristics of passive and depassi- vated steel. In addition, concrete has to be defined as an electrolyte allowing transport of ions between anodic and cathodic reaction sites. The models proposed to describe the corrosion process are based on different approaches, using well-defined polarisation curves for the anodic and cathodic polarisation behaviour of steel reinfor- cement. In most instances for passive steel only the cathodic polarisation behaviour is of interest, whereas for depassivated steel both the anodic and cathodic polarisation behaviour are required. The Laplace equation is commonly used to calcu- late the distribution of anodic and cathodic current densities at the steel-concrete interface and the po- tential distribution in the concrete electrolyte. How- ever, this approach requires realistic a priori as- sumptions on the spatial distribution of anodic and cathodic areas at the steel surface and the asso- ciated polarisation behaviour, as well as the spatial distribution of concrete resistivity. More detailed in- Materials and Corrosion 2006, 57, No. 8 DOI: 10.1002/maco.200603899 603 www.wiley-vch.de/home/wuk F 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim