Abstract
UDC 621.359.3
DOI https://doi.org/10.5281/zenodo.1053749
The process of electrodeposition of copper platings on mild steel products has been analyzed. The causes of poor adhesion of the platings from the acid and alkaline non-cyanide electrolytes are revealed. It is shown that the problem of direct electrochemical deposition of a copper plating on a steel base of non-cyanide electrolytes is due to the conjugated process of the contact exchange in the copper ions – iron system. Plating with good adhesion can be obtained only if the contact exchange process is stopped at the initial stage – until the steel substrate under the pores of the sediment is subject to significant grinding. In acid electrolytes, adhesion is poor because of a high value of the contact exchange current. In alkaline non-cyanide electrolytes, iron is passivated and the adhesion of the coating is insufficient because of the presence of a separating passive film at the base-coating interface. In neutral electrolytes, it is possible to obtain a coating with good adhesion to the substrate, but the results are not stable due to a low buffer capacity of the solution. When a copper plating is applied from acid electrolytes using a pre-nickel plating operation, a thin nickel sublayer has pores through which the contact exchange process proceeds. It is shown that to obtain platings with good adhesion, the nickel sublayer should be of a minimum thickness of 3–5 microns.
Keywords: copper electroplating, copper electrolyte, aminocomplexes, adhesion to substrate, mild steel, contact exchange.