Simultaneous holographic, ellipsometric, and optical imaging of pitting corrosion on SS 316LVM stainless steel

Digital in-line holographic microscopy, a three-dimensional imaging technique, is incorporated for simultaneous usage with the previously established surface sensitive optical imaging techniques, ellipsomicroscopy and microscopy. This addition allows volume reconstructions of the solution in the vicinity of the working electrode with microscopic resolution, and particle tracking. Holography is also sensitive to local variations in the solution concentrations; estimations of the index of refraction can be made using the interference patterns alone. These three optical techniques complement each other and simultaneously provide information about changes in the oxide layer, pit developments, and local solution changes during electrochemical testing of stainless steel.

► Digital in-line holographic microscopy DIHM with ellipsomicroscopy for surface imaging. ► DIHM can track particles ejected during pitting corrosion into the electrolyte. ► DIHM detects local changes in index of refraction due to pitting events. ► Combining three optical techniques and standard electrochemical measurements. ► The local volume affected is dependent on the max. anodic current for a pitting event.