Corrosion of reinforcing steel embedded in kaolinite clay was studied for a two year exposure period. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (POL) revealed a decrease of the corrosion rate (CR) of the steel bars up to average values of 2.5 μm y −1 . X-ray photoelectron spectroscopy (XPS), and Scanning electron microscope (SEM) equipped with Energydispersive X-ray spectroscopy (EDX) techniques showed the formation of a thick and compacted corrosion layer composed of several iron oxides, namely, Fe 2 O 3 , Fe (OH) 2 , Fe 3 O 4 and FeCO 3 . The external corrosion product is composed mainly of magnetite (Fe 3 O 4 ) and siderite (FeCO 3 ). EDX mapping showed a homogeneous distribution of the elements across the cross-sectional of the corrosion layer.