Study on initial corrosion behavior of bogie steels with ferrite plus pearlite and granular bainite structures immersed in sulfur-containing environment

The corrosion behavior of bogie steel with two different structures immersed in a sulfur-containing environment for 12 h was studied, including ferrite + pearlite structure (the heating temperature is 1473 K, the final rolling temperature is 1123 K, the final cooling temperature is 873 K, and the cooling rate is controlled at 7-9 K/s) and granular bainite structure (the heating temperature is 1223 K, keep warm for 2 h, cooling in water is 10 min, the cooling rate is greater than 100 K/s). The results show that there is no significant difference in the initial corrosion rate between ferrite + pearlite and granular bainite structures. The former is affected by the microregion galvanic effect and local residual stress to jointly promote corrosion initiation, while the latter has a uniform distribution of local residual stress on the surface, which is the main factor for corrosion initiation. After the sample is immersed, a dense thin rust layer quickly forms on the surface, blocking O-2 in the solution, resulting in the dissolution of the ferrite matrix of the two structures is mainly affected by the reduction of H+ and SO32-/SO42-.