Kelvin Probe Force Microscopy and Atmospheric Corrosion of Cold-rolled Grade 2205 Duplex Stainless Steel

The effect of cold deformation on the corrosion behaviour of duplex stainless steel is not fully understood. The work reported in this paper addresses the effect of cold-roll reductions of up to 40% on microstructure development and corrosion behaviour of grade 2205 duplex stainless steel. The deformation heterogeneity and microstructure after cold-rolling as a function of process direction has been analysed by electron backscatter diffraction (EBSD). These microstructure sites were then investigated using Kelvin Probe Force Microscopy (KPFM) and subsequently targeted with MgCl2 salt-laden deposits to probe their corrosion performance in controlled atmospheric environment. In the as-received microstructure the ferrite was preferentially attacked, whilst the austenite became more susceptible to localised corrosion with increasing cold deformation. Interestingly, Volta potential differences measured between a Pt-probe and the surface also changed with the degree of cold deformation. Volta potential hot-spots obtained by KPFM seemed to correlate with regions containing plastic strain.