Study on the Occurrence State of Lanthanum in Rust Layer and Mechanism of Its Influence on Invasion State of Corrosion Atoms

Rare earth elements have unique outer electronic structure, variable valence, and strong chemical activity; however, their occurrence state in the rust layer and influence on the invasion state of corrosion atoms are still unclear. Herein, using a combination of experiment and first‐principles calculation, the occurrence state of La in the rust layer of low‐alloy high strength steel, the phase composition, compactness and stability of the rust layer, and the invasion state of corrosion atoms before and after La alloying are studied. The results show that La exists in the corrosion products in the form of a solute atom. La increases the concentration of corrosion‐resistant elements Cr and Mo in the rust layer but does not change the phase composition. La is conducive to stabilizing Cl atoms in α‐FeOOH and β‐FeOOH, so as to protect the steel matrix from Cl. La atoms inhibit the dissolution of Cl atoms into γ‐FeOOH and Fe 3 O 4 structures and hinder their formation.