Effect of addition of alumina and rare-earth oxide particles on the corrosion resistance and mechanism of low carbon low alloy steel

Abstract

The corrosion mechanism of the low carbon low alloy steel with Al₂O₃ particles and rare Earth (RE) oxide particles was compared in a simulated marine environment. It is shown that when the Al₂O₃-containing particles are introduced, the number density of nonmetallic particles of the steel increases twice, and the average particle size decreases from approximately 2.4 μm to 1.4 μm. With the introduction of Al₂O₃-containing particles, the amount of pitting corrosion increases. Furthermore, pitting corrosion occurs more uniformly owing to the fineness of the Al₂O₃ particles, thereby leading to smaller, shallower pits after the Al₂O₃ particles are shed. Hence, the corrosion performance of the steel with Al₂O₃ particles is significantly improved than that of the steel without Al₂O₃ particles. By adding RE oxide particles into steel, the nonmetallic particles in steel are refined but not as effectively as that achieved by adding the Al₂O₃-containing particles. Different from Al₂O₃ particles, Cu is obviously enriched in the location of RE oxide particles at the initial corrosion stage, which makes the steel exhibit the best corrosion resistance. Cu enrichment is attributed to the mobile Cu present in the rust layer and to the micro acid region formed around the RE oxide particles.