Abstract-In order to collect information for the manufacture and application of a designed dual lefthanded material (LHM) structure, the influence of salt spray test on the two conductive composite coatings consisting of silver and copper is contrastively investigated. It is found that the salt spray corrosion test can influence the microstructure of the coated copper and silver layers, leading to the decrease of electrical conductivity of the coated copper and silver layers. As results, the transmission performance of the dual-LHM structure is reduced, while the bandwidth of the dual-LHM structure is broadened. Moreover, at the same conditions, the salt spray corrosion test has less influence on the transmission characteristics of the silver-plated dual-LHM structure than those of copper-plated dual-LHM structure.