Effect of non-stationary current regimes on the morphology of silver electrodeposits

Abstract

This work is concerned with the use of reverse current regimes in order to form small-grained and compact silver deposits during the electrorefining process. Several parameters were varied, i.e., i) anodic overpotential, ii) cathodic vs. anodic time ratio and iii) duration of the anodic pulse. After optimization of these parameters, phosphate ions were added and the electrolyte was stirred. The effects of a rise of the anodic overpotential on the grain sizes of the silver deposit and compactness were studied. Prolongation of the anodic time had a similar influence but with a decrease in current efficiency. An increase of the cathodic vs. anodic time ratio caused an enlargement of the grains and a decrease in the compactness of the deposit. Optimal morphological characteristics were obtained when PO3-4 were added and the electrolyte was stirred.

Rad se bavi korišćenjem reversnih strujnih režima za dobijanje sitnozrnih i kompaktnih taloga srebra u procesu elektrohemijske rafinacije. Varirano je nekoliko parametara: a) anodna prenapetost, b) odnos vremena trajanja katodnog i anodnog pulsa i c) trajanje anodnog pulsa. Nakon optimizacije ovih parametara, u elektrolit su dodati fosfatni joni i primenjeno je mešanje elektrolita. Ispitivan je uticaj anodne prenapetosti na veličinu zrna taloga srebra i na njegovu kompaktnost. Produženje trajanja anodnog pulsa pokazalo je sličan efekat, ali uz smanjenje iskorišćenja struje. Povećanje odnosa vremena trajanja katodnog i anodnog pulsa dovelo je do povećanja zrna i smanjenja kompaktnosti taloga. Optimalna morfologija taloga je dobijena nakon dodatka PO3-4 i uz mešanje elektrolita.