Effect of RE on corrosion resistance of weathering steel ASTM under marine atmospheric environment

Because of its strong ability of deoxidation and desulfurization, RE are often used as purifiers for steel. RE improves the corrosion resistance of weathering steel ASTM mainly by changing the existing state of inclusions in steel, reducing the number of large inclusions, refining grains and reducing the source of corrosion.

The corrosion resistance of Q345B RE steel containing trace rare earth cerium (Ce) and lanthanum (La) in simulated marine climate was investigated by laboratory accelerated corrosion test. It is found that the properties and morphologies of inclusions in weathering steel ASTM have changed, resulting in the reduction of sulphide inclusions and the reduction of pitting sources. Moreover, the dissolution of Fe2+ can dissolve the rare earth inclusions. Because the trivalent rare earth oxides are alkaline, especially those of Ce group elements, the dissolution of rare earth sulfur oxides can increase the pH value of the micro-solution and the corrosion potential of Fe. At the same time, the hydrolyzed Ce3+, La3+ bind to the OH - of the cathode and precipitate in the cathodic polarization region, playing the role of precipitation film corrosion inhibitor.

The effect of Ce/La mixed RE on the corrosion resistance of carbon structural steel in marine atmospheric environment was investigated. The results show that the corrosion potential of weathering steel ASTM with rare earth is negatively shifted, the self-corrosion current density decreases, and the cathodic reaction is hindered. RE play the role of cathodic corrosion inhibitor, thus improving the corrosion resistance. With the increase of rare earth content, the rust layer of test weathering steel ASTM after periodic wetting corrosion test becomes denser, the thickness decreases, and the cracks and voids decrease obviously.