An experimental study using a three-point bending test on RC beams with dimensions of 150 x 280 x 3000 mm, naturally corroded over many years was conducted to evaluate the influence of steel corrosion on structural performance and, in particular, to better understand the change in ultimate deflection in bending and then in ductility. Some previous works by different authors are also discussed. The results show that the conventional ductility factor hardly applies to the assessment of ductile behaviour of corroded beams. A new ductility factor, based on the ratio between ultimate deflection of corroded and non-corroded beams, is proposed. In addition, the relation between ductility factor of corroded beams and cross-section loss in the corroded reinforcing steels was studied on the RC beams tested. The service life of corroded structures appears to be limited by the reduction of ductility in bending behaviour, which is more pronounced on the reduction of load-bearing capacity. This was linked to the change in mechanical properties of corroded steel bars in comparison with non-corroded steel bars. (c) 2014 Elsevier Ltd. All rights reserved.