AC GRAINING OF LITHOGRAPHIC SHEET IN HYDROCHLORIC-ACID

The present investigation deals with the parameters which influence the uniformity of the surface during the AC graining of AA1050 aluminium cold rolled sheet in hydrochloric acid. In particular, the effects of the current density and of the acid concentration on the surface topography are investigated. The surface is characterized by brightness of the resulting sheet, by roughness, by the surface topography and by the surface increase. Different mechanisms of roughening are observed, called 'graining' and 'etching. These mechanisms can be distinguished by capacitance measurements. It is shown, that a uniformly grained surface can be obtained by the suitable combination of current density and acid concentration. Two types of smut are observed, which determine the brightness of the sheet.