An example of corrosivity prospection by geophysical electrical direct current methods for a bridge foundation:
An example of corrosivity prospection - example of measured earth current graphs:
The corrosivity prospection includes determination and statistical evaluation of the intensity of the earth current electric field.
For its measurement we use two (perpendicularly spred) pairs of non-polarizable electrodes(ABEM Pb-PbCl or CU-CuSO4).
An example of the geoelectrical section - determination of rock resistivity necessary for the corrosivity evaluation:
The corrosivity prospection includes also the rock resistivity determination in the subsoil
usually by VES. There are resistivities by VES marked (back color), current densities (green color) and the corrosivity classification(ČSN 038372)(red color) in the figure with the section example on the right.
(The most corrosively dangerous layer is determinig for the final evaluation.)
An example of the situation with resulting vectors of earth electrical field and current density values:
The resulting corrosivity of subsoil is determined according to surface geoelectrical
measurements results and possible set of other lab measurements (agresivity of underground water etc.).
(in terms of ČSN 03 8372). Points of VES and non-polarizable electrode positions are marked if violet color.
The final corrosivity prospection results are tabulated accordig to ČSN 038372 and Technical specifications of the Czech Ministry of Transport and Communications TP 124.