The durability of MgO/hydromagnesite mortars was studied with respect to their corrosion performance and resistance to chloride attack and moisture. Rapid chloride ingress measurements showed chloride migration coefficients of \({D}_{\text{Cl}}={1\times 10}^{-13}\) to \({1\times 10}^{-12}\) \({\text{m}}^{2}/{\text{s}}\) . MgO/hydromagnesite pastes were cured in alkaline chloride solution to investigate the formation of Mg-chlorides; however, no such phases were observed. The corrosion rate of carbon steel embedded in MgO/HY mortars, as determined by linear polarization resistance measurements, was in the range \({i}_{\text{corr}}=1\times {10}^{-9}\) \(\text{A/}{\text{cm}}^{2}\) in dry and \(1\times {10}^{-7}\) \(\text{A/}{\text{cm}}^{2}\) in wet conditions, irrespective of the mortar composition or curing condition. These findings corroborate the hypothesis that, in the absence of chlorides, the moisture condition is the primary predictor of corrosion rate of carbon steel in the MgO/hydromagnesite binder. These accelerated, short-term experiments suggest that the binder may be suited to protect embedded carbon steel from corrosion under specific exposure conditions of practical relevance.
