The corrosion of steel rebar in concrete can be caused by the corrosive Cl- in marine environment, and adding inhibitors is an effective way to suppress the corrosion. As a kind of green inhibitor, sodium silicate has been widely used in protection of Fe, Zn, Mg, Al and their alloys. Nevertheless, the inhibition mechanisms of sodium silicon are controversial because of the various experimental conditions, such as the ratio of Na2O∶SiO2, concentration of sodium silicon, pH values, temperature, presence of oxygen, etc. Particularly, the studies focusing on the effect of sodium silicon concentration on corrosion resistance of steel rebar are relatively deficient. This could be probably because that as coagulants, silicate compounds are essential additives, and their solidification is of primary concern, while the effect of corrosion inhibitor on metal surfaces is often neglected.