Numerical analysis of topographic and Volta potential profiles during corrosion of duplex stainless steel in chloride solution

Abstract

Corrosion of duplex stainless steels (DSS) usually initiates at a specific phase, causing preferential phase-dissolution in aqueous environments. Although the scanning Kelvin probe force microscopy (SKPFM) can characterise the phase-corrosion at a micro- or even nanoscale, conventional data-processing methods are insufficient to analyse massive data to derive mechanistic information, and sometimes, even cause a misunderstanding of corrosion evolution. Here we utilised root mean square, power spectral density and fractal evaluations to analyse the time-dependent topographic and Volta potential results obtained by SKPFM during corrosion progression of 2205 DSS in a chloride solution. Corrosion of the DSS preferentially occurs in the ferrite phase and at the ferrite/austenite boundaries in the initial stage. The corrosion changes from the initial galvanic mechanism to mass transfer control with increased time. By using proper numerical tools, the Volta potential results are more insightful of analysing corrosion than the topographic profiles.