Recently new developments on the determination of the corrosion forms have been achieved due to necessity to predict long-term corrosion behavior of low carbon steels. For the nuclear industry in France it has been decided to store the nuclear waste in a deep geological repository that has to be safe for periods of several thousand years. As the wastes confined in glassy matrix could be put in low carbon steel containers in contact with clay, it is necessary to determine the alteration behaviour of these different materials in contact with each other. The long periods required limit the interest of laboratory simulation that cannot produce on short periods representative alteration interface without accelerating the degradation conditions. That is why archaeological artefacts have been studied because they provide thick corrosion layers formed in natural conditions. Over recent years a specific methodology has been set up by combining microbeam analytical tools in order to determine the elementary composition and phase structure of the corrosion scales formed on archaeological artefacts corroded in different media (atmosphere, concrete and soils).