Pitting corrosion of duplex and austenitic stainless steel using grey-scale image analysis

Pitting corrosion of type AISI 316L ((UNS S31603) and Uranus 52N+ (UNS S32550) stainless steels immersed in a 3% NaCl aqueous solution at pH 2.5 and 5.0 has been studied using image analysis. The topography of representative corroded areas has been obtained using scanning-electron microscopy (SEM) after anodic polarization experiments, and transformed into grey-scale images. The distribution of grey scale has been analysed, and the average grey scale of images and the integral of current density of pitted areas have been calculated. The higher the current density, the smaller the average grey scale of the images. The three-dimensional plots have been restored according to the grey scale of the pitted areas, and their corrosion characteristics have been analysed.