Measurement methods and fractal dimensions of blast-cleaned steel substrates

Morphological parameters of steel substrates determine the adhesion of coatings and adhesives. Three different assessment methods (cross section image, contact stylus instrument, and stripe light projection) were applied to blast-cleaned substrates. A total of 12 surface configurations were generated with different abrasive materials. The fractal dimensions were estimated by means of the box-counting method. Design of experiment and ANOVA were applied to statistically analyze the relationships. Factors included abrasive type, surface preparation grade, surface roughness, and surface profile measurement method. Similar relative trends for the fractal dimensions resulted for the three measurement methods. The normalized values of the fractal dimensions were approximately twice as high for the cross section profiles compared to the ones from contact stylus and stripe light projection. Fractal values derived from contact stylus measurements showed the highest repeatability, whereas those derived from cross section images showed the lowest repeatability.