Study Of Preparation And Corrosion Behavior Under Cold Rolling On Ni-Co Alloy Electrodeposition Coating

Nickel electroplating is utilized widely with good advantages such as strength, toughness and corrosion/wear resistance as well as mechanical properties.The applications of such deposits fall basically into made lamps and lanterns, cars, batteries, priting three main categories: decorative, functional and electroforming. In recent years, Ni-Co alloys have been studied extensively for magnetic applications especially in microsystem technology for the manufacture of sensors, actuators, microrelays and inductors. These alloys have been deposited from a variety of simple and complex baths. Investigations on electrodeposited Ni-Co alloys have indicated that their properties strongly depend on the cobalt content. However, the content of cobalt in the Ni-Co deposit can be controlled by experimental parameters, such as electrolyte composition, pH, current density, temperature and stirring speed.Deeply-draw steel strip with nickel electrodeposited coating is a newly high-property material for battery shell, which is produced with nickel coating deposited on low-carbon steel and followed with some special optimum treatment. Moreover, the applications of Ni-Co deposit on deeply-draw steel strip are expected. As a result, the corrosion resistance and microhardness were improved especially.The studies of this master thesis contain two main parts. (1) The amount of cobalt in the Ni-Co deposit by altering the experimental parameters such as electrolyte composition, current density, temperature, was studied and analyzed. (2) The effect of the electrolyte composition and operating parameters on the corrosion/wear resistance, microhardness, internal-stress and the resistor of the deposit was studied respectively. In addition, the effect of rolling reduction on the corrosion resistance was investigated.In the first chapter, the research background and research status related were introduced at first. Then the background of this master thesis was interpreted. In the second chapter, the nickel-cobalt alloy coatings were obtained by different experiment parameters. In the third chapter, the weight percent content of cobalt in the deposit was estimated by EDX analysis. The analysis revealed that the amount of cobalt in the deposit was significantly higher as compared to that present in the electrolyte, which is a characteristic of anomalous co-deposition. In addition, the effect of the current density and temperature on the properties of the deposits was discussed in detail. In this paper, an important conclusion was drawn that the deposits were refined when the content of cobalt sulphate increased from 0 to 2g/L in the electrolyte, and then the hardness and the tensile strength were developed slowly. In the third chapter, the effect of cold rolling reduction on the corrosion resistance of the deposits was investigated.