Microfabrication methods have been used to construct crevice formers of rigorously controlled gap and length. These have been used to study the IR-controlled crevice corrosion of Ni200 in 0.5 M H2SO4 to determine the effect of crevice gap (G) on the position of the accelerated attack (x(crit)) within the crevice. The experimental results were then compared to the results of computational studies. This comparison demonstrated that over a wide range of gaps, the fundamental, controlling scaling factor is x(crit)(2)/G. Finite crevice lengths led to a distortion of the potential and current distributions at larger gaps in both the experimental and computational studies. Such distortions can occur at gaps as low as 2% of the crevice length. The time dependence observed for x,,it is determined primarily by the evolution of the electrolyte composition rather than the increase in surface area of the active area due to dissolution. (C) 2004 The Electrochemical Society.