Improving Corrosion Resistance of 3Ni Weathering Steel in Simulated Tropical Marine Atmosphere via Changing Microstructure

The initial and long-term corrosion behaviors of 3Ni steels with different microstructures including ferrite (F), ferrite + bainite (F + B), and bainite (B) were studied. The results showed that the corrosion process of steels can be divided into an initial state and a stable state, and the corrosion rates increased continually in the initial stage and gradually decreased in the stable stage. Due to the larger relative potential difference between the F and B in the F + B steel, the corrosion rate was the highest among three steels. The B steel first formed the protective rust layer and presented the best protectiveness. The initial corrosion of B steel mainly developed longitudinally and led to small and deep corrosion pits. The initial corrosion of the F and F + B steels mainly developed laterally, and was contributing to the large and shallow corrosion pits.