A study on the surface severe plastic deformation and corrosion behavior of an interstitial free steel

In the present work, a Ni-stabilized interstitial free (IF) steel was subjected to severe plastic deformation (SPD) in order to attain nanograin structure. To do this, a different technique so-called brushing was used. This technique is very cost-effective, simple and practical. For brushing process, different brushes made of brass, stainless steel and low carbon steel were used. The processing parameters such as brush rotational speed, different shapes and dimensions of the brush wire, the amount of brushing and applied load were adjusted so that to attain the desirable structure. The surface and microstructural evolutions were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The thickness of the nanostructure surface layer formed by brushing was about 40-50 m with a maximum microhardness of about 540 Vickers. The formed nanostructure layer had a grain size of 30-50 nm. In order to study the effect of nanograin structure on the corrosion behavior, the samples, brushed under different conditions, were subjected to corrosion testing and the related polarization curves were obtained using 3% NaCl solution. The comparison of the polarization curves of brushed and non-brushed samples indicated that the peak of polarization curve of brushed sample, exhibited a larger potential difference and a lower current density comparing to not-brushed case. The larger potential difference and the lower current density mean greater corrosion resistance and lower corrosion rate. A quantitative comparison between the current density of the two samples revealed a 55% increase in corrosion resistance for the brushed sample as compared to not-brushed counterpart.