Abstract: An electrochemical cell was devised to investigate corrosion electrochemical behavior of metal underneath thin electrolyte film in atmosphere. The Piontelli's type of Luggin-Haber capillary was inserted from the backward of working electrode. The results show that, cathodic process on Cu is mainly affected by the thickness of the electrolyte film of 0.5 mol/L HCl +1 mol/LNa2SO4 aqueous solution and its anodic dissolution changed from Tafel region to limiting diffusion current.Moreover, the corrosion potential of Cu in due media will increase with decrease of the thickness of the film.