Cathode Polarization Potential during Electro‐deposition of Copper: I . Nonreproducibility in Acid Copper Sulfate Solutions

Abstract

The constant stats polarization potential (C.S.P.) of the cathode during the electrodeposition of copper from copper sulfate‐sulfuric acid solutions depends upon the conditions of preparation and storage of the solution and the time which it is kept after preparation.Freshly prepared solutions usually give fine deposits, associated with high C.S.P. values, but on Keeping there is a decrease of C.S.P. value, accompanied by a coarsening of the crystal structure. The C.S.P. value is raised again, and a fine structure deposit obtained, after the solution has been treated with oxidizing agents or submitted to prolonged electrolysis. Evidence has Been obtained that this effect is due to the presence in the reagents, or to formation during storage of the solution, of a very slight trace of impurity which has the unusual property of reducing the C.S.P. value and increasing the crystal size in the deposit. The formation of this impurity is associated with traces of contamination in ordinary distilled water, and a method for the preparation of solutions which remain stable for several months has been developed.