Thin layers (ca 1 micron thickness) of aluminum are applied to the surface of pure zinc and iron substrates using PVD. In the case of Fe, samples are subsequently heated to between 300C and 650C to produce atomic interdiffusion and Al-Fe intermetallic formation. In the case of Zn, no heat treatment is applied and no intermetallics form. PVD coated substrates are overcoated with 30 microns of polyvinyl butyral (PVB) and subject to corrosion-driven organic coating (cathodic) disbondment in a standard "Stratmann" experiment using 5% aqueous NaCl. The time-dependent potential profiles associated with delamination are recorded using a Scanning Kelvin Probe (SKP) and analyzed to determine delamination rates. On both Zn and Fe the PVD Al layer is found to profoundly block cathodic oxygen reduction and hence cathodic disbondment. On Zn this effect is uncomplicated by other delamination mechanisms and PVD Al seems a practicable approach to improving disbondment resistance. On Fe, unalloyed Al is rapidly consumed in an anodic (filiform) delamination process. Filiform is not seen for heat treatment temperatures >300C but as these increase between 300C and 650C through diffusion of Fe atoms re-introduces electrocatalytic activity for oxygen reduction and cathodic disbondment rates increase towards that for pure Fe.