Corrosion monitoring with speckle correlation

摘要

The changes in the microtepegraphy of a metal surface during a corrosion process are measured by decorrelation of the scattered speckle fields under coherent illumination. For that purpose a quantitatire relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and refiectivity changes of point scatterers at the surface. The speckle fields are recorded by a CCD camera and processed numerically in a computer, yielding the standard deviation of the tepegraphy Changes with nanometer sensitivity. From the analysis of a series of images taken at equal time intervals during the corrosion process, the de degree of interrelation among subsequent topography Changes is calculated.