Electrochemical impedance spectroscopy was used to study the corrosion behavior of reinforcing steel embedded in alkaline activated fly ash mortar with chloride pollution. The porous nature of the rust layer was studied using a transmission line model and the parameters of the interfacial oxide/hydroxide film were determined by interpretation of the impedance data using a cylindrical pore. The rust layer generated on the steel surface was studied at the end of the experiment (two years) using scanning electron microscopy and X-ray diffraction. (C) 2014 The Electrochemical Society. All rights reserved.