On Etching of Silver by the Graphite-Suspension Method in 0.5M Sulfuric Acid Solution

Abstract

The etching of silver by the graphite-suspension method based on an anodic electroxidation of graphite particles existing in the suspension state in 0.5M sulfuric acid solution was investigated. Silver which belongs to metals of the nobler electrode potential, is able to be etched excellently by the graphite-suspension method. The etching velocity of silver increases with making fine graphite particles, with increasing concentration of suspension graphite and furthermore with elevating temperature. The etching velocity within this experimental region of the suspension potential becomes faster with increasing total surface area of graphite particles striked against silver plate. The etching ability represented by the etching velocity divided by the apparent surface area of graphite in the unit volume of suspension increases with increasing concentration of graphite, but decreases with decreasing diameter of graphite particles. The etching silver takes place according to a local cell reaction consisting of Ag→Ag⁺+e as anodic reaction and reductions of the products on the anodically oxidized graphite particles as cathodic reactions.