Abstract: The system includes means for cyclically putting into operation a circuit for controlling and regulating a DC generator connected between the structure to be protected which constitutes a cathode and the anodes of a group of anodes which are insulated from the structure and are in contact with the electrolyte in which said structure is placed. The circuit includes means for reading the potential provided by a reference electrode, for calculating the potential difference between the structure and the electrode potential as read, and for comparing the calculated potential difference with upper and lower thresholds. The value of the voltage output from the generator may be adjusted by means in steps of predetermined value as a function of the comparison signals delivered by the comparator. The system is particularly applicable to protecting underground or underwater metal structures from corrosion.