Abstract
The Hydroson system is a novel cleaning system which has recently been adopted to solve cleaning problems in many industries, particularly in metal finishing. Although effective the fundamental principles and mode of action of the process are not fully understood. In this work, the Hydros on system was quantitatively evalued and compared with other methods of cleaning. Further, the mechanism of cleaning was studied and was shown to be due to the scouring action produced by the impingement of the high pressure jets on the contaminated surface. The rate of cleaning was comparable with ultrasonic cleaning at a frequency of 13 KHz and intensity of 520 Wm[-2]. The effect of Hydroson agitation was studied on the electrodeposition process using an alkali zinc electrolyte with and without addition agents. Hydroson agitation reduced the diffusion layer thickness at the cathode to a similar value compared with ultrasonic agitation, and gave many beneficial effects on the properties of both the electrolyte and the deposit. It reduced cathodic and anodic polarization, increased the cathodic current efficiency and maximum current density, thus allowing good quality deposits to be obtained even at higher current densities. The deposit from the zincate bath without addition agents was less porous, had a finer crystallite structure and was harder than those formed from solutions with no agitation, with magnetic stirring to give a flow rate of 20 cm s[-1], or with ultrasonic agitation. In the zincate bath with addition agents, Hydroson and ultrasonic agitation increased the hardness, but reduced the brightness of the deposit. Hydroson agitation was also shown to increase the rate of electrolytic recovery of zinc metal from dilute zincate solutions by 3-4 fold compared with magnetic stirring. The flow velocity of solution across a surface in the centre of the Hydroson tank was determined by a theoretical and experimental approach and was found to be approximately 1.2 ms[-1].