EFFECT OF MULTI-PASS COLD ROLLING ON THE CORROSION PROPERTIES OF 2101 DUPLEX STAINLESS STEEL

Duplex stainless steels (DSS) are increasingly employed in the industry based on their combination of good mechanical properties and high corrosion resistance. These properties are achieved by stabilising quasi-equal volume fractions of the austenitic and ferritic phases at room temperature. The pitting resistance of a DSS is influenced by its chemical composition, presence of second phases, heat treatment, grain size, cold working, as-well-as surface roughness. In this research, LDX 2101 (EN 1.4162) lean DSS is investigated at different grades of cold deformation (thickness reduction from 9% to 61%), obtained by multi-pass cold rolling. The effect of this type of cold-working method on the corrosion properties of the material was evaluated by means of potentiodynamic polarization tests at room temperature in 3.5 wt.% NaCl solution and of critical pitting temperature (CPT) evaluation in 1 M NaCl solution. The results of the corrosion tests were also linked with proper OM and SEM microstructural observation and with results of XRD tests. The results showed that the multi-pass cold rolling does not affect the corrosion properties of the investigated material with deformation steps that are <10%. Corresponding to this finding, the microstructural and phase analysis investigations proved that no strain-induced martensite was formed during the process. The obtained results were also compared with single-pass cold-rolled properties of the material from a previous study pf the authors. As an effect of single-pass cold rolling, the same DSS (LDX2101) suffers a significant decrease of the CPT and destabilisation of the protective oxide layer with the thickness reduction. Therefore, this research shows that it is advisable to use multi-pass cold rolling instead of the single-pass method to reach high deformations without the deterioration of corrosion properties.