ELECTROCHEMICAL POLISHING OF DECORATIVE PRODUCTS FROM COPPER ALLOY

Abstract

Copper is a soft and fusible metal with good electrical and thermal conductivity, ductility, malleability and resistance to oxidation in air. Pure copper and its alloys are widely used in various industrial fields: in construction, automobile and instrument making, and in the field of electrical engineering. More than half of all mined metal goes to the production of electrical appliances and power transmission. The high level of ductility led to the use of copper for the production of decorative and jewelry items. Copper has excellent bactericidal properties, which is why it is very popular in medical and food industries.

Copper alloys, especially brass, have significantly better properties than copper. The mechanical strength of brass is higher and is well machined than pure copper. Products made from copper alloys are very relevant for the manufacture of jewelry and decor items.

When exposed to aggressive environments, copper and its alloys corrode, become covered with copper oxide, and the luster fades. Polishing of copper products is very relevant to improve anti-corrosion properties and give a mirror finish. Copper with a polished surface is not subject to corrosion in dry air, the oxide layers have no color, there is no tint effect.

The presented article introduces the results of electrochemical polishing of an alloy of copper and zinc grade L90 (brass) in a phosphate electrolyte with the addition of various organic substances. For copper of this grade, the reflectance value of about 70% was obtained experimentally, with the addition of thiourea. The technology of pre-treatment of brass samples before the electrolysis process was also established. For this purpose, in addition to mechanical processing, the samples were degreased and subjected to etching. The surface of the polished copper was examined using an atomic force microscope (AFM).