Characterisation of pitting corrosion by white light interferometry Børge Holme a, * , Otto Lunder b a SINTEF Materials and Chemistry, P.O. Box 124 Blindern, NO-0314 Oslo, Norway b SINTEF Materials and Chemistry, Richard Birkelands v. 3 A, NO-7465 Trondheim, Norway Received 10 March 2005; accepted 24 April 2006 Available online 9 August 2006 Abstract An improved method is described for obtaining detailed information on the size and shape of many corrosion pits by examination with White Light Interferometry. The entire surface is first imaged at low resolution by automatically stitching individual images into one composite image. Specially written software analyses the image and determines the location of all corrosion pits. The program then guides the white light interferometer in making high resolution topographic images of each pit. The images are analyzed to give any desired data about the pit geometry, such as depth, maximum width, projected area, volume, etc. Curves showing the depth distribution for each pit can be generated along with detailed topographic images of all pits. The technique does not work for pits that undercut the surface, and there is a practical size limit of about 20 cm 2 . The method is therefore best suited for studying the early stages of pit propagation. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: A. Aluminium; B. White light interferometry (WLI); C. Pitting corrosion 1. Introduction Examination and evaluation of pitting corrosion is commonly performed by use of an optical microscope to determine the size and density of pits [1]. This technique is well 0010-938X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2006.04.022 * Corresponding author. Tel.: +47 98 28 39 46; fax: +47 22 06 73 50. E-mail address: borge.holme@sintef.no (B. Holme). Corrosion Science 49 (2007) 391–401 www.elsevier.com/locate/corsci