Quantitative topography characterization of surfaces with asymmetric roughness induced by AC-graining on aluminium

In this article a method is presented for characterizing the topography of surfaces with asymmetric roughness by analyzing topographic maps from interferometry measurements. For creating appropriate surfaces with asymmetric roughness, electropolished aluminium samples were electrograined by alternating current (AC) in hydrochloric acid. A pitted and convoluted surface with different extent of non-attacked areas (plateaus) and different pits height distribution was developed by using the AC-graining. Thus, surfaces with different extent of negative asymmetric roughness were developed by this technique. The shift induced by the asymmetric roughness between the mean surface level (MSL) and the true surface of the sample was estimated by the respective histograms of the height distribution. Subsequently, the histograms were corrected in order to identify the MSL with the true surface level. By the deconvolution with fitting of the corrected histograms, the extent of the plateau areas and the pits height distribution taking into account the true surface level of the sample were estimated. On the other hand, the extent of the plateau areas was also calculated by the percent data cut at the zero level of the respective corrected bearing ratio curves. Further, this method for correcting and analyzing roughness measurements in order to achieve the topography characterization of surfaces with asymmetric roughness is also applicable on industrially produced lithographic printing plates. In addition, this method could also be applied to other types of applications where the topography characterization of surfaces with negative asymmetric roughness is an important engineering factor.