High speed nickel plating on difficult to plate metal(Aluminium)

摘要

Aluminium has been widely used in many field of application due to the low density, sensitive to corrosion, high mechanical strength and ease of fabrication. Plating of metal on aluminium is complex and difficult because aluminium always reacts with air to form oxide. It is difficult to obtain a good adhesive property on the aluminium surface. Thus, to plate metal on the aluminium, oxide layer must be eliminated by using an intermediate pre-treatment. However, this process involves several steps and even then the level of addition between the plated metal and the aluminium part is poor. The object of this project was to investigate the possibility of plating nickel directly on aluminium surface without any pre-treatment process, investigating the level adhesion between the deposited nickel and the aluminium base by high speed electroplating technique and also to investigate the effect of current density, temperature and different type of solution on weight of plated sample, thickness of plated sample and rate of deposition. The level adhesion of the nickel coating was determined qualitatively by using Adhesion Testing while morphology and thicknesses of Ni plated was studied using Scanning Electron Microscopy (SEM). It was found that the level of adhesion between nickel and aluminium became low at current density above 1.0 A/cm2 and Ni plated was found to peel off easily. Besides, by increasing the current density and temperature the weight and thickness of Ni plated increase and sulphate based Ni solution gave much higher rate of deposition compared to the traditional Watt’s based solution by increasing the current density and temperature.