The anodic dissolution of Pd in halide-free sulfuric acid, catalyzed by a single adsorbed layer of iodine, was studied with a Pd(100) single crystal that contained an ordered c(2x2) iodine adlattice. Experimental measurements were based upon ultrahigh vacuum electrochemistry (UHV-EC), an approach that combined voltammetry, coulometry, low-energy electron diffraction, and Auger electron spectroscopy. It was found that Pd dissolution occurred only when the surface was pretreated with iodine. More significantly, the surface coverage and structure of the iodine adlattice were unaffected by the corrosion reaction, an indication that the anodic dissolution process occurs essentially one interfacial metal-layer at a time.