CALCULATION OF THE IMPEDANCE OF NONCYLINDRICAL PORES .2. EXPERIMENTAL-VERIFICATION ON PORES DRILLED INTO STAINLESS-STEEL

The method of one-dimensional modelling of the pore impedance is validated on pores drilled in AISI 316 stainless steel. Impedance measurements were carried out in 0.5 M sulphuric acid solution. Experimentally, it is found that, for cylindrical pores with a radius/pore length-ratio smaller than 0.5, the one-dimensionality condition is satisfied. Furthermore, impedance measurements on noncylindrical, scaled-up pores provide evidence that a geometric constant Lambda(g) has to be introduced, as in Part I. In accordance with this theory it is found that for pores with narrowing cross section Lambda(g) is less than 1/3, while for pores with a broadening cross section Lambda(g) is greater than 1/3. Moreover, it is shown that the matrix method, presented in Part I, provides a way of calculating the impedance of a noncylindrical pore by using a highly reduced number of discs, N, compared to the recursion method of Keiser et al. This is an advantage in fitting procedures.