β Scribed by K. Ogura; H. Wada
No coin nor oath required. For personal study only.
Iron passivated chemically in chromate solutions over a range of pH was electrochemically reduced in phosphate-borate buffer solution of pH 8.5. According to the chronopotentiometry, the passive fllm became thinner as the pH diminished, which was in agreement with the ellipsometric result. The rest potential became more positive with decreasing pH, and the pH dependence was -0.11 V/pH and -0.07 V/pH in acid and alkaline solutions, respectively. The shift of the rest potential towards more positive values didnot lead to an increase in the thickness of the passive film, and in this it differs from the behaviour of the passive film formed anodically. This discrepancy can be rationalized by the idea that most of the potential drop appears not across the passive film, but at the passive film-solution interface. In chemical passivation, a positive shift of the electrode potential is not associated with the growth of the passive film, provided that the rest potential is more positive than the Flade potential. The most influential factor for passive film growth is the environment, in which the iron initially dissolves readily and the passive film retains its stability.
π SIMILAR VOLUMES
With the apparatus described it was possible to measure under potentiostatic conditions at frequencies up to about 1 kHz spectral densities of current noise comparable to the thermal noise at resistances of the order M Ohm. The spectral densities of the current noise at passive iron microelectrodes
Cobalt-57 was electrodepositcd on mild steel, and lhe hlb;ssbnuer spectrum of the Fe-57 formed by electron capture observed before and after passivation with KzCrOj solution. After passivntion Fe(II[) species were observed, and the low recoilless fraction indicated a poorly crystalline film. The sur
## Abstract The effect of some phosphonic acids (HMEP, NTMP, HEDP) on the chemical passivation of iron by dissolved oxygen in neutral aqueous solutions has been investigated. It has been shown that in the presence of phosphonic acids chemical passivation cannot be attained. This effect is due to th