Determination and Control of Metallic Impurities in Alumina Deposits Obtained by Aqueous Electrophoretic Deposition

Electrophoretic deposition (EPD) is a suitable manufacturing method for depositing thin and thick films onto conducting materials. Usually, EPD is performed in organic vehicles, where handling difficulties and health hazards are important problems. These difficulties can be solved using aqueous suspensions; however, the high voltages that develop during EPD increase the rate of hydrolysis and galvanic reactions. As a result, pores or metallic contamination can be retained in the ceramic deposit. The deposition of Al2O3 onto zinc electrodes in water is described in this work. The formation and characteristics of Al2O3 deposits and the effect of Zn2+ contamination have been studied as a function of the processing conditions (current density and deposition time) and the slurry properties (dispersing state and solids content). A neodymium:yttrium aluminum garnet (Nd:YAG) laser, coupled to an inductively coupled plasma spectrometer, has been used to determine the contamination profile in the ceramic coatings. By controlling the intensity of the electric field applied to the slurry, as well as the slurry conductivity and solids content, the contaminating effect of the electrode can be reduced significantly.