Browsing by Author "Mahmood, Mahmood Hameed"

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.

Transfer of copper metal by boiler feed water from the condenser tubes to other critical equipment parts of the industrial plant, like steam turbine blades, boiler tubes, can cause serious problems, such as reduction of electricity generation in power plants, boiler failure, and increase production costs, which may ultimately lead to loss of economic viability. Among the factors which affect the corrosion rate of copper alloys in flowing water environments, the relationship between the velocity of feed water and the corrosion rate of copper alloy has not been studied in detail. Therefore, this study investigates the effect of the flow rate of water on the corrosion of copper alloy at different combinations of temperature (between 20 and 45 ºC) and dissolved oxygen concentration (between 6.1 and 9.2 mg/l). All other operating condition variables which have effect on flow rate were also considered. The effect of different flow rates on copper alloy corrosion, such as laminar, transition, and turbulent flows, were investigated. It was found that the flow rate condition has a significant effect on the protective copper oxide layer in the inner surface of copper alloy tubes. Surface metallographic characterization by FESM, SEM, and EDX, demonstrated that the copper oxide surface layer cannot withstand the turbulences at the beginning of the turbulent flow condition, while the oxide layer erosion is much less during fully developed turbulent flow condition. Therefore, the corrosion rate values is maximum during the initial phases of the turbulent flow condition, but becomes very low at fully developed turbulent flow conditions associated high water velocity. This indicates that the overall flow rate conditions, which include physical properties of the fluid, hydrodynamic parameters, and dimensions of the pipe, have the dominant influence on corrosion rate.