In concentrated hydrochloric acid solutions, the overall dissolution rate depends on the acid concentration. Using mixed electrolytes (HClNaCl) we have established the influence on the overall anodic stationary current, of each of the H + and Cl − ions. Considering the logarithmic derivative of the overall current with respect to the activities in the various constituents of the medium reveals the complexity of the reaction mechanism especially in the activity and passivation ranges.