Abstract Steel reinforced concrete is the most commonly used composite material in construction; however, large amounts of energy, natural resources are required for its manufacture and is susceptible to corrosion in the presence of aggressive environments. However, there are alternatives aimed at sustainable development, through the gradual replacement of ordinary cement with other Supplementary cementitious materials. Consequently, the present investigation evaluates the effect of fly ash and granulated blast furnace slag on the electrochemical phenomena of steel bars, embedded in a cement paste matrix, characterized by scanning electron microscopy, X-ray fluorescence and area surface to establish variations in electrochemical phenomena evaluated by Tafel extrapolation curves, half-cell potential, resistance to linear polarization and electrochemical impedance spectroscopy. The electrochemical conditions show that the surface areas and composition affect the passivation degree; therefore, mixtures with FA generate passive protection and on the contrary, the mixture with GBFS does not present any type of corrosion protection.