Effect of Cr on Characteristic of Rust Layer Formed on Low Alloy Steel in Flow-accelerated Corrosion Environment

Abstract

The flow-accelerated corrosion experiments were carried out to research the effect of Cr on the rust layers formed on the carbon steel and Cr-containing steel, as well as the structure of rust layer of the two experimental steels. The influence of Cr on the flow-accelerated corrosion resistance and the corrosion morphology of inner rust layer formed on the Cr-containing steel were studied by the methods of polarization curves, scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscope. The distribution of Cr and its form of existence in the inner rust layer were analyzed. The results show that corroded mass loss of Cr-containing steel is lower than that of carbon steel and its inner rust layer is compact. Cr exists in the form of Fe₂ CrO₄ and is enriched in the inner rust layer. This concentration could make the inner rust layer exhibit the tendency of amorphous. This phenomenon is related to fine Fe₂ CrO₄. The inner rust layer becomes more compact because of the formation of fine Fe₂ CrO₄, and the protectiveness of inner rust layer could be improved remarkably.