The effect of microstructure on the initial corrosion behavior of low carbon steel in simulated coal solution

Abstract

The service life of weathering steels in wagon body was determined by their corrosion resistance directly. This study investigated the influence of microstructure on the initial corrosion behavior of low carbon steels, systematically. The initial corrosion behavior of ferritic-bainitic (F+B) steel, bainitic (B) steel and ferritic-pearlitic (F+P) steel are thoroughly analyzed using coal leach solution immersion test, macroscopic and microcircuit electrochemical methods. The results revealed that F+B steel exhibited the highest corrosion resistance, with the potential of M-A islands surpassing that of ferrite. The initial corrosion initiates from the dissolution of the ferrite matrix, followed by detachment of the M-A islands. The potential of M-A islands is higher than that of bainitic ferrite lath, and the corrosion originates from ferrite dissolution in B steel. Moreover, F+P steel exhibited the largest potential difference between pearlitic and ferrite, leading to initiation of corrosion from the pearlitic corrosion of internal ferrite. Additionally, the multiphase characteristics of P in F+P steel exacerbates their corrosion susceptibility. Overall, the influence of microstructure on the initial corrosion behavior of low carbon steels can be attributed to the potential difference between different phases. Ferrite is the preferentially dissolved phase due to its negative potential difference.

Keywords

• initial corrosion
• low carbon steel
• microstructure
• electrochemistry
• coal leaching solution