The surface quality of extruded aluminium sections is often a key characteristic in determining customer acceptance. The present paper presents the results of a study which consisted of 108 production runs of an AA6061 alloy extrusion. The volume of each run is measured as the number of 99 cm billets processed before the extrudate surface roughness exceeded a threshold value. Melt chemistry, particularly Mg, Si, and Zn content are shown to be significant in determining production volume. Scanning electron microscopy and X-ray analyses reveal that the presence and nature of MgO are the key determinant of production volume.
