Alkali-activated fly ash (AAFA) is considered as a promising alternative to ordinary Portland cement (OPC). However, the lack of calcium hydroxide in AAFA leads to an increased susceptibility to carbonation, thereby resulting in a decreased alkalinity of pore solutions in AAFA and significantly impacting the stability of steel passive films. To improve the corrosion resistance of steel in carbonated AAFA environments, sodium citrate was used as an environmentally-friendly corrosion inhibitor with three carboxylate groups. In this context, the corresponding electrochemical behavior of steel exposed to carbonated AAFA solutions with different concentrations of citrate was studied. In spite of the detrimental effect on the initial passivation behavior, sodium citrate was found to effectively improve the corrosion resistance to chloride attack for steel owing to a synergistic inhibition effect of adsorption film and precipitates on the steel surface. In addition, the correlation of citrate concentration and inhibition mechanism in carbonated AAFA solutions was revealed.