An Al-Co-Ce alloy coating has been developed for an AA2024-T3 substrate that can serve as barrier, sacrificial anode, and reservoir to supply soluble inhibitor ions to protect any defect sites. In this paper, the chemical throwing power of such an Al-Co-Ce metallic coating under thin electrolyte films representative of atmospheric conditions is modeled. The geometry is that of an Al-Co-Ce surface with the presence of a scratch simulating exposed AA2024-T3. The model calculates the time necessary to accumulate Ce+3 and Co+2 inhibitors over the scratch when released from the Al-Co-Ce coating under different conditions. The model factors in the pH-dependent passive dissolution rate of an Al-Co-Ce alloy to define the inhibitor release flux. Transport by both electromigration and diffusion are considered together. The effects of scratch size, initial pH, chloride concentration, and electrochemical kinetics of the material involved were studied. Sufficient accumulation of the released inhibitor (i.e., the Ce+3 concentration surpassed the critical inhibitor concentration over AA2024-T3 scratches) was achieved within a few hours (e.g., similar to 4 h for scratches of S = 1500 mu m) when the initial solution pH was 6 and the coating was adjacent to the AA2024-T3. (c) 2006 The Electrochemical Society.