Abstract: The invention relates to the continuous or discontinuous analysis of the corrosive effect of the soil and the environment on a buried metallic structure (such as an underground gasoline storage tank for retail gas stations). The apparatus includes a measuring system having a sensor with at least one Cu/CuSO.sub.4 electrode to which a metallic electrode containing iron is secured at least one voltmeter, and optionally at least one current generator; at least one data display and acquisition system consisting of at least one amplifier, at least one analog-to-digital converter, at least one magnetic recorder and at least one display unit for the read-out of these data on the site, these belonging to the group formed by the numerical display devices and the electromechanical recorders; and a system for the processing of these data consisting of data-processing computing means.