The present work aims at evaluating the ability of cerium and lanthanum conversion pre-treatments applied on galvanized rebars to hinder the cathodic process of hydrogen release during the early stages of contact between the rebar and the high alkaline environment of the concrete pores solution. The electrochemical behaviour was assessed by polarization resistance, open circuit potential and scanning vibrating electrode technique (SVET). The chemical composition and the morphology of the pre-treated surfaces were evaluated by X-ray photoelectron spectroscopy and scanning electron microscopy. The substrates were immersed in solutions simulating the concrete interstitial electrolyte. The pH was 13.2. For these conditions, the results showed that conversion pre-treatments based on cerium or lanthanum nitrate did not hinder hydrogen evolution, but they changed the corrosion processes occurring on the galvanized rebar during the early stages of immersion.