Synergistic corrosion inhibition of tartrate and phosphate on reinforcing steel in chloride-contaminated carbonated alkali-activated fly ash

Alkali-activated fly ash (AAFA) is a low-carbon binder with considerable application potential. However, its susceptibility to chloride attack and carbonation compromises the corrosion resistance of reinforcing steel, and the application of corrosion inhibitors in AAFA remains unclear. To address the aforementioned challenges, the synergistic inhibition performance of sodium tartrate (ST) and sodium phosphate (SP) on chloride-induced corrosion of reinforcing steel in carbonated AAFA solutions was investigated using electrochemical measurements, morphology characterization techniques, and quantum chemical calculations. During the short-term corrosion stage (1 h), an optimal ratio of the composite corrosion inhibitors consisting of ST and SP was determined in both carbonated and non-carbonated AAFA solution and saturated calcium hydroxide (CH) solution. During the long-term corrosion stage (20 d), steel exhibited high corrosion resistance in the chloride-contaminated AAFA solution, whereas steel was severely corroded in the AAFA solution under the combined action of chloride attack and carbonation. However, at the optimal ST/SP inhibitor ratio, the composite corrosion inhibitors effectively mitigated the active corrosion of steel in carbonated AAFA solution. On the basis of quantum chemical calculations, a synergistic inhibition mechanism of ST and SP for steel in chloride-contaminated carbonated AAFA solution was proposed. © 2026 Elsevier Ltd.