Corrosion Behavior of Weathering Steels with Different Contents of Rare Earth Elements La and Ce

The effects of different contents of rare earth (RE) elements Ce and La on the corrosion behavior of weathering steel Q355NHq were investigated with alternate immersion tests and electrochemical measurements. The corrosion rates were lowest with the rusted steels containing 170 ppm RE elements. Aspex analysis showed that steels with the RE elements content of 170 ppm had the greatest percentage of inclusions with high content of RE elements. The immersion tests showed that modified inclusions with a high percentage of (RE)xOy exhibited a better corrosion resistance than CaS-Al2O3 inclusion. Compared with steels containing no more than 90 ppm RE, the rust layers of steels containing 170 ppm RE elements were compact and contained high amounts of α-FeOOH and low amounts of γ-FeOOH. Based on the results obtained, the influence of the different contents of RE elements in weathering steel corrosion is discussed.