Ohmic Compensation in Desert Soil Using a Galvanostatic DC Bridge

A modified wheatstone bridge circuit has been used with success to compensate ohmic interferences in soil and other high resistivity corrosive solutions during galvanostatic (current controlled) dc measurements. Previous applications of the circuit have been reviewed and details of operation described. The most current use in our laboratories has been a study of corrosion in desert soils at the Nevada Nuclear Test Site (NNTS). A profile of desert soils samples with depth was obtained for electrochemical testing of lead and steel, which are construction materials for low level nuclear waste containers at NNTS. The soils were of naturally high resistivity, requiring compensation of ohmic interferences during electrochemical polarization measurements for corrosion rate (polarization resistance) determinations and cathodic protection requirements. Results are described briefly on effects of sulfate, chloride and carbonate, all of which can be derived from variations of soil composition with depth. Effects of added moisture content on all soil samples are also discussed.