Corrosion Behavior of Q355NHq Steel: Effect of Alloying with Different Concentrations of Rare Earth Elements (Ce and La)

The effects of different contents of rare earth (RE) elements Ce and La on the corrosion behavior of weathering steel Q355NHq were investigates with alternate immersion tests and electrochemical measurements. The corrosion rates were lowest with the rusted steels containing 170 ppm rare earth elements. Aspex analysis showed that steels with the rare earth elements content of 170 ppm had the greatest percentage of inclusions with high content of rare earth elements. The immersion tests showed 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 rare earth elements were compact, and contained high amounts of -FeOOH and low amounts of γ-FeOOH. Based on the results obtained, the influence of the different contents of rare earth elements in weathering steel corrosion is discussed.