Quantified three-dimensional imaging of pitted aluminium surfaces using laser scanning confocal microscopy

Abstract

Scanning confocal light microscopy offers an alternative three-dimensional imaging technique that can allow a fresh view of surfaces. It can image samples that are wet, coated, or porous and cope with highly irregular surfaces for which the desired depth of field is difficult to study by other methods. Its principal attraction is the quantification of surface topography. At Alcan International, confocal microscopy has been examined as an alternative to scanning electron microscopy parallax techniques in the quantitative understanding of surface critical samples. This paper describes the use of the Bio-Rad MRC-600 laser scanning confocal microscope to image aluminium surfaces in various surface conditions, including as rolled and corroded. Two- and three-dimensional images were produced using the control software supplied with the confocal microscope. However, it was easier to process these images to form quantitative projections that were transferred to a Kontron Ibas image analysis system. On the image analysis equipment, images were examined for measurement of surface roughness, surface area, and apparent volume. The relative benefits, and drawbacks, of these alternative techniques and algorithms devised for the analysis of surface topology are compared and discussed in the context of studies of corroded aluminium samples.