目的 研究20SiMn低合金钢表面对3.5% NaCl溶液中不同硅酸钠浓度的响应机制，揭示硅酸钠作用下金属表面的缓蚀机理。方法 采用开路电位、动电位极化曲线、电化学阻抗谱和Mott-Shottky曲线测试样品表面的耐蚀性能和硅酸钠的吸附行为，并通过SEM观察浸泡后的样品表面形貌，使用EDS和XPS分析腐蚀产物的元素和成分。结果 随硅酸钠浓度的增加，20SiMn钢存在从活性溶解向表面钝化的演变过程，在所研究的浓度范围内，缓蚀效率在含有0.012 5 mol/L硅酸钠的氯化钠溶液中到达最高值(95.92%)。当添加硅酸钠缓蚀剂后，20SiMn钢表面可形成一层由铁氧化物和SiO2组成的复合膜层，其中SiO2的吸附方式以物理吸附为主导，且随着硅酸钠浓度的增大，表面产物中Si含量逐渐降低。XPS分析表明，样品表面产物逐渐从单一的FeOOH转变为Fe3O4和FeOOH的混合物，而FeOOH对SiO2具有更强的亲和力，Fe3O4则相对较弱，因此高硅酸钠浓度下的产物不利于SiO2的吸附。此外，高浓度硅酸根离子的水解引发了溶液中OH^–浓度的升高，水解产生的不溶性硅醇结构相互之间形成了交联结构，致使发挥缓蚀作用的吸附态SiO2的量降低，复合膜层的致密性降低。结论 硅酸钠对3.5% NaCl溶液中20SiMn 低合金钢的腐蚀存在缓蚀作用，但由于腐蚀产物的组成变化和缓蚀剂本身的水解作用，在形成钝化的前提下，硅酸钠浓度不宜过高。

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.