MoO2-4抑制AISI304不锈钢局部腐蚀的机理

采用X射线光电子能谱（XPS）研究了AISI34不锈钢在含（MoO^2-4 Cl^-1）的模拟闭塞电池中形成钝化膜的组成与结构及MoO^2-4、CrO3、CrCl3、CrOOH、Fe2O3、γ-FeOOH、Fe(OH)3、CrO^2-4、Cr(OH）3、NiCl2、FeCl2和FeCl3；溅射5min时膜内层主要有MoCl3、CrO2、FeCl2、FeCl3以及少量的FeO，MoO^2-4对钝化膜的影响在于；MoO^2-4迁入闭塞区后吸附在金属表面上，可取代或部分取代吸附在钢表面的Cl^-，并与Fe^2 在蚀孔内反应生成不容性的FeMoO4而沉积到蚀孔壁上，有助于蚀孔的再钝化，从而抑制腐蚀的进一步扩展；MoO^2-4的吸附能使水合氧化亚铁沉淀膜由阴离子选择性变为阳离子选择性，使H^ 可以从膜下扩散出去，而Cl^-1难以扩散到膜下富集，从而使MoO^2-4具有缓蚀作用。

MECHANISM OF MoO42- RETARDING THEDEVELOPMENT OF THE LOCAL CORROSION IN 304 STAINLESS STEEL/Cl- SOLUTION

XPS analysis was used to study the composition and structure of passive film of 304 stainless steel in Simulated Occluded Corrosion Cell(SOCC) containing MoO42- + Cl- and the retarding function and inhibiting effect of MoO42- to local corrosion. The effect of MoO42- to passive film is found, MoO42- was absorbed in the surface of metal when it migrated into Occluded Corrosion Cell (OCC) to replace or partly replace Cl- absorbing in the surface of steel, and to react with Fe2+ producing dissolved FeMo04 depositing in corrosive hole, contributing to repassive of corrosive hole, and retarding propagation of corrosion; The absorption of MoO42- resulted in transform of the hydrateferrous oxide deposition film from anions selection to cation selection and diffusion of H+ out from film, and it is difficult to diffuse for Cl- into film to rich, so MoO42- had inhibiting function.