Lap joints fabricated using Al2024T3/commercially pure Ag sheet couples with nylon fasteners were exposed to standard field tests in a tropical marine atmosphere for a total period of six months. Atmospheric conditions were recorded using a weather monitoring station. Simultaneously, samples were also exposed in a salt spray chamber according to ASTM B117 and GM 9540P standards. Corrosion data was obtained for monthly intervals for both field and laboratory samples. Weight loss, pitting characteristics and the nature of the corrosion products were evaluated. Corrosion mechanisms based on the observed atmospheric corrosion phenomena are proposed.