Surface topography parameters as a correlation factor for liquid droplet erosion test facilities

Abstract

An evaluation of six different coatings was completed in a set of inter-laboratory tests, involving three rain erosion test facilities. Results from two whirling arm type test facilities and one water-jet test facility were compared in the test campaign. The materials and coatings that were investigated included clad aluminium alloy, paint coatings, polyurethane tape, plasma vapour deposited thin film and sol–gel coating. The surface topography of the test coupons was measured using a confocal laser scanning microscope. Using the primary profile of the surface, a comparison was made based on the incubation time or time to failure in the case of coatings. Correlation factors were estimated between the three test facilities. A comparison of the surface features and the surface topographical parameters lead to correlations for two different impact velocities at two of the facilities. Cross correlations between facilities and impact velocities were also shown with this method to within 20%. The incubation period was the main measure of the resistance of the coatings to rain erosion.