M. Asanuma et R. Aogaki, NONEQUILIBRIUM FLUCTUATION THEORY ON PITTING DISSOLUTION .2. DETERMINATION OF SURFACE COVERAGE OF NICKEL PASSIVE FILM, The Journal of chemical physics, 106(23), 1997, pp. 9938-9943
Following part I, in this paper, the experiments for nickel pitting di
ssolution in NaCl solution were carried out to compare the theoretical
equations with experimental data. From the theoretical examination on
nonequilibrium fluctuations in part I, after double-layer charging cu
rrent, a slow relaxation current, i.e., the diffusion current of the f
luctuations was expected. The current must have been a function of pas
sive film coverage. Therefore, if the passive him breaks so slowly, su
ch diffusion current cannot be observed. However, it was actually foun
d that the film is rapidly broken at the final stage of the double-lay
er charging, and the coverage is determined by the slope of the Cottre
l plot of the diffusion current. Then, it was also shown that in the a
bsence of Cl- ions, the film have already been broken at least about 1
5%, which may be attributed to the passivity breakdown effect of H+ io
ns. Finally, by the use of extrapolation of the data to the infinity o
f Cl- ionic concentration, the average critical concentration fluctuat
ion without any passive film was obtained. (C) 1997 American Institute
of Physics.