High strength steels in concrete structures used as reinforcement have high durability. The corrosion resistance is due to the physical barrier that concrete provides, and by a protective passive film developed on the surface by the high alkaline media. In presence of chloride ions, they can break the passive film. These ions can be found into the mixing water or in the structures near marine environment. The current work studies corrosion phenomena of drawn wire steels with eutectoid composition containing a pearlitic microstructure, which is composed by a ferritic matrix with cementite layers observed by Atomic Force Microscopy. An electrochemical cell with three electrode is developed in order to assemble it into Atomic force Microscopy (AFM) and topography images are obtained a long of the electrochemical experiments in continuous. This work is focused on the study, by Electrochemical Atomic Force Microscopy (EC-AFM), the early stages of the corrosion of such steels as a consequence of their exposure to a sodium chloride solution. The topography images show the pearlitic microstructure of the steel, with a preferential attack of the ferritic phase and the Cementite acting as a cathode. Depth histograms provides the corrosion loss of the ferritic core. Taking into the account the passivity of the cementite phase, it is possible to estimate the corrosion rate. At the same time, the electrochemical results gave us the corrosion rate by the lineal polarization technique. According to the Farady¿s law it is possible to obtain the corrosion depth. Therefore, topographical values and electrochemical values are compared during a period of time.

Trabajo presentado en el VI International PhD Student Workshop: Durability of Reinforced Concrete from COmposition to Protection, celebrado en Delft (Países Bajos), los dñias 4 y 5 de julio de 2013