A chloride-sensitive corrosion sensor and protector made of an optimized Mg-Al alloy for reinforcing steel

[Display omitted] •The Mg-Al alloy with 17 wt% Al is the best corrosivity sensor and corrosion protector.•Excessive Al content in the Mg-Al alloy triggers hydrogen embrittlement of steel.•The corrosion mechanism of the Mg-Al alloy changes with increasing Al content.•The intelligence level of the Mg-Al alloy may be modified by its surface area . The smart detection of concrete-corrosivity and the intelligent protection of reinforcing steel provided by Mg alloys with various Al contents were systematically investigated in a reconstituted concrete pore solution (RCPS). The results indicated that increasing the Al concentration of the alloy up to 17 wt% could enhance the performance of corrosivity-detection and the corrosion-protection. However, excessive Al alloying could lead to an over-protection of the steel. The optimized Mg-Al alloy sensing and protecting anode was also verified in mortar prisms. Based on these findings, the anodic behaviors of Mg-Al alloys in the RCPS were analyzed.