Monitoring and Measuring Pitting Corrosion of Stainless Steel by Holographic Interferometry

Abstract In the present investigation, an optical corrosion-meter has been developed for materials testing and evaluation of different corrosion phenomena. The idea of the optical corrosion-meter was established based on principles of 3D-holographic interferometry for measuring rnicrosurface dissolution, i.e, mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e, corrosion current of metallic samples in aqueous solutions. In the present work, an early stage of pitting corrosion of a stainless steel and a carbon steel in seawater was monitored in situ by the optical corrosion-meter during the cyclic polarization test. The observations of pitting were basically interferometric perturbations detected only on the surface of the stainless steel in seawater. The interferometric perturbations interpreted as a localized corrosion in a form of early pittings, of a depth 0.3 to several urn.Consequently, results of the present work indicate that holo-graphic interferometry is very useful technique as a 3D-interferometric microscope for monitoring pittings at the initiation stage of the phenomenon for different metallic samples in aqueous solutions.