SEM images with different magnification of an anodised aluminium substrate (250 V, 0.125 Abold dotcm−2, 3 min) after a treatment with the He-plasma jet. Before the treatment, the substrate was covered with a gold layer of 50 nm thickness. The SEM image on left hand side shows two deep erosion traces with and without a formation of an afterglow phase (plasmoid). An erosion activity of plasmoids on the treated surface can form separated eroded areas, which are presented on the right hand side. Deep erosion traces of microdischarges are marked with dashed circles in the right image.