抄録
For the purpose of studying the electrochemical properties of sprayed Al coating on steel, the influences of surface exposure prior to immersion, solute concentration, surface grinding and stirring solution upon separate Al electrode (purity 99.85% sheet) and Fe electrode (0.05C mild steel sheet) in aerated 3.3N KCl solution using a vacuum tube voltmeter and a 3.3N KCl calomell cell, were first examined.
It was found that the behavior in the stagnant solution each of Al electrodes exposed for some time at a temperature of 25°C to 300°C after polishing with emery-paper No. 0/4 exhibited the similar one to that obtained in the case of the bare (as polished) Al electrode in the stirring solution, and the electrode potential value was-0.83 volt (3.3N KCl cal. scale) in a steady state almost immediatery after immersion. This value corresponds closely to the first stage steady state potential of the bare Al electrode for 30 minutes' immersion in the stagnant solution.
The electrode potential behavior of Al-Fe couples in the stagnant aerated solution was investigated by placing together a sheet of Fe as polished and a sheet of Al as polished back to back to ensure metallic contact and then this couple electrode with vinyl tape. which was demonstrated to be the most suitable by a series of investigation upon sealing effect of materials such as paraffin, cellophane, etc.,
The ratio Al area/Fe area was changed by covering the exposed metallic surface with sealing vinyl tape, and electrode potential-time curves were plotted for each ratio of 1-3×10-4/1.
It was found that in all cases the electrode potential reached steady -0.83V almost immediately after immersion, and that when anodic area forms 0.03 per cent of the total electrode area, almost all self-polarization is cathodic and the electrode potential is anodically controlled.
