Acidic dissolution of ferritic stainless steels is simulated using the ab initio based Monte Carlo technique. This approach aims to reach a better understanding of the effect of alloying elements on the acidic dissolution of SS at the microscopic scale. The dissolution probability of a surface atom is shown to depend drastically on the number and chemical nature of its nearest neighbors in dense emerging crystallographic planes. A "critical coordination number" (CCN) is defined, above which the dissolution probability is too low to contribute significantly to the dissolution rate, and below which the dissolution events are too fast to be experimentally detected. For pure alpha-Fe and FeCr alloys this CCN was found to be equal to 4. Increasing the Cr concentration does not change the CCN but decreases the interatomic bonding energy, making the dissolution process easier. The addition of Mo is found to involve multiple CCN, belonging to different crystallographic orientations, which results in a substantial decrease of the dissolution kinetics. (C) The Author(s) 2016. Published by ECS. All rights reserved.