Electroplasma Purification of Copper Using Tannin as a Corrosion Inhibitor

The paper presents a method for cleaning corroded copper using an electric plasma discharge in a “solid anode–liquid cathode” system. The proposed approach differs from traditional chemical methods in increased environmental friendliness due to combination of plasma treatment of the metal and the use of corrosion inhibitor (tannin) introduced into the liquid cathode. The experiments were performed on copper samples with corrosion damage, which served as a solid anode. The liquid cathode was an electrolyte consisting of aqueous solution of ammonium sulfate with concentration of 2%, supplemented with tannin (1 and 1.5%), prepared on the basis of technical grade water containing 0.02% calcium ions. In the presence of calcium ions, tannin forms a dense adhesive layer on the metal surface, helping to protect the surface from subsequent corrosion damage. During the study, the characteristics of electrical plasma discharges were measured, the dynamics of gravimetric parameters associated with corrosion damage were traced, and the microscopic condition and surface roughness were assessed using profilometry, which made it possible to identify optimal process parameters. Analysis of the results showed that plasma treatment with addition of tannin as a corrosion inhibitor improves the protective properties of the cleaned surface. This study demonstrates for the first time the potential of combined use of plasma treatment in the presence of natural corrosion inhibitors for development of environmentally friendly technologies for cleaning and anti-corrosion protection of metal surfaces.