低合金钢筋在水泥萃取液中钝化膜的耐蚀机理研究

Corrosion Resistance Mechanisms of Passive Films Formed on Low Alloy Rebar Steels in Liquor of Cement Extract

采用动电位极化曲线、Mott-Schottky结合XPS和AES,分析研究了Cr对耐蚀钢筋在水泥萃取液中形成的钝化膜的耐蚀机理。结果表明,随着浸泡时间的延长,钢筋电极的自腐蚀电流密度(Icorr)降低,浸泡1 d后可以形成具有保护性的钝化膜。Cr含量的增加减小了钢筋钝化膜中的载流子密度,提高了其稳定性。Cr含量的增加抑制了Fe2+向Fe3+的氧化过程,从而提高了钢筋钝化膜的耐蚀性。耐蚀钢筋中的Cr参与了钝化膜的形成,稳定钝化膜则主要由Fe的氧化物组成;钝化膜内层为含Cr-Fe的氧化物,外层为Fe的氧化物;钝化膜的厚度在3～4 nm之间,随Cr含量的增加而略微增大。

Influence of Cr content on the corrosion resistance of passive films formed on low alloyed rebar steels in liquor of cement extract was studied by means of electrochemical techniques, X-ray photoelectron spectrometer and auger electron spectroscopy. The Icorrof steel electrodes is found to decrease with increasing immersion time, and protective passive films could form after 1 d immersion. The increase of Cr content decreases the carrier density of the passive films, thereby improves their stability.The increase of Cr content inhibits the oxidation process of Fe2+to Fe3+, thus enhance the corrosion resistance of the passive films. Stable passive films are primarily consisted of iron oxides with a thickness of3~4 nm. As Cr is involved in the formation of passive films, which induces the formation of an inner layer of complex Cr-Fe oxides beneath the outer layer of Fe oxides. The film thickness slightly increases as the content of Cr increases.