CORROSION BEHAVIOUR OF ANNEALED 42CrMo4 STEEL

In this paper, the corrosion behaviour of 42CrMo4 low-alloy steel after normalizing, soft annealing, spheroidizing annealing and full annealing is investigated. 42CrMo4 is steel for quenching and tempering, and one of the widely used and studied steels due to its good combination of mechanical properties. Sometimes, it is used in the annealed condition. Nevertheless, the corrosion properties of 42CrMo4 steel are poorly studied, especially in the annealed condition. The main objective of this work is to increase the knowledge about the corrosion behaviour of the investigated alloy. The mechanical and microstructure properties of the samples after different annealing processes were characterised with hardness testing, optical and scanning electron microscopy (SEM) and X-ray diffraction (XRD). Measurements of the open-circuit potential and potentiodynamic polarisation of the samples after different annealing processes were carried out in a naturally aerated solution. It was found that the corrosion rate of the soft annealed samples was higher than that of the spherical and full annealed samples. Moreover, full annealing resulted in a significant improvement in the corrosion resistance.