Assessment of metallic structures in contact with an electrolyte

A method for assessing a structure arranged in an electrolyte, the method comprising the steps:

• connecting an electric source between the structure and an earth;
• imposing, on the structure, a primary current with at least three frequencies comprising a first frequency of a first duration and of a first amplitude, a second frequency of a second duration and of a second amplitude and a third frequency of a third duration and of a third amplitude;
• wherein a series of currents with the first frequency, the second frequency and the third frequency are separated by a time gap;
• measuring of fields with an instrument comprising at least a first sensor, a third sensor and a fourth sensor and a positioning system;
• wherein each sensor is configured to measure a field along the structure for each of the at least three frequencies;
• and
• computing at least one primary field resulting from an electric current within the structure based on the measured field.