CORROSION MECHANISM UNDER ACCELERATED ATMOSPHERIC CONDITIONS

Corrosion experiments, which were conducted under accelerated atmospheric conditions, are presented and discussed. A salt spray chamber (Alternative Climate Test Chamber type SC-450) equipped with a saltwater tank and water or steam injector was chosen for this purpose. Series of ferrous and non-ferrous materials were subjected to a controlled corrosion lasted at least 4 and at maximum 12 days. As parameters the temperature of the test room and the temperature of the humidified air were chosen. The as corroded specimens after a rough observation with optical microscope (Olympus 60) were examined by means of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Results are discussed on the basis of passivity of the films of corrosion products formed on the surface of the specimens and their breakdown and a mechanism is proposed. According to this, in spite that protective films are formed during oxidation process, these films do not ensure a sufficient protection to the materials, as corrosion mechanism and especially pit corrosion propagation destroy the continuity of the passive films