Development of anodized copper coating in oxalate containing solution and its characteristics

Abstract

Copper oxide recently was used in various scientific applications like gas sensors, hydrophobic surfaces, solar cells, catalysts, and data storage devices. Development of copper oxide characteristics becomes one of the challenges in the materials science. This research develops a hard corrosion resistance coating for enhancing the corrosion resistant of copper to eliminate corrosion industrial problems. It studies nano copper oxide coating using the anodization technique in oxalate containing solution. Anodization process was conducted using linear sweep voltammetry (LSV) technique in solution contains oxalate. The anodizing parameters were selected in the ranges of, 0.1 - 0.5 M oxalate concentration, 0 - 24 °C bath temperature and 7.5 - 9 v voltage. The study investigates the characteristics of this coating. This includes investigating coating microstructure, hardness, in addition to the hydrophobicity, thermal and electrical resistivity and corrosion behaviour. The grain size, porosity and thickness of the anodized coatings were investigated by field emission scanning electron microscopy (FESEM). The phases, microstructures, crystal size, and chemical compositions of the coating were characterized using x-ray diffraction (XRD), and (EDX). Results show that nano structures of cupric CuO and cuprous oxides Cu2O were formed on the coated surface. The effects of the anodizing parameters on the characteristics of the coatings were evaluated. It was obsearved that maximum anodization resistance and minimum critical current recorded at the lowest temperature and highest oxalate concentration, with the lowest anodizing rate, and charge transferred through coating of less porous and maximum hardness. The microstructures investigation using FESEM revealed that grain sizes of the anodized coating was in the range between 25 to 68 nm. The average grain size of the coating formed at the lowest temperature and highest oxalate concentration was around 43 nm with maximum thickness of 17 µm, maximum hardness of 186 Hv and lowest porosity of 0.59 %. The results also showed that the anodized coating improves the corrosion resistance in solutions of 3.5% sodium chloride and 2 mg/l ammonia according to weight loss, tafel extrapolation, and electrochemical impedance spectroscopy methods. These results refers to the effects of anodized coating in electrical insulation and inhibition for the charge and ions transfer.