Electrical resistance method

The electrical-resistance method involves passing an electric current through the structure and exploring the surface with voltage probes. Flaws, cracks, or inclusions will cause a disturbance in the voltage gradient on the surface. Railroads have used this method for many years to locate transverse cracks in rails. 

An electrical resistance methods which directly measures loss of metal from a probe installed in the corrosive system under study is described in Section 19.3. It is reported that corrosion equivalent to a thickness loss of as little as 2-5 X 10 cm can be detected . This technique is most useful as a means of monitoring steps taken to reduce corrosion, e.g. by inhibitors, or to detect changes in the corrosivity of process streams. Electrical methods of determining corrosion rates are considered subsequently. 

The proton conductivity of the perfluorosutfonic acid membranes greatly changed by the gamma-ray irradiation in air at room temperature. The conductivity at 300 K, measured in air using the electrical resistance method... 

It is also a measure of the moisture stress in plants or soil, measured in megapascals. A more negative value indicates greater moisture stress. Soils with no moisture stress have a water potential of 0 to -1 mPa. Two methods of measuring soil water potential are the heat-dissipation method or the electrical-resistance method. 

In principle the theory of electrical capacitance can be applied to the determination of lubricant film thickness between the bounding surfaces of two solids, but in practice the geometrical difficulties described in Section 5.1.1 for electrical resistance methods are even more troublesome for capacitance. If the solids are bounded by two flat surfaces parallel to each other, the electrical capacitance problem becomes that of a parallel-plate condenser, for which the formula is... 

The electrical resistivity method of subbottom exploration/surveying is based on the relationship/correlation between the conductivity of soils and rocks and the ion concentration in their pore waters. The resistivity is, therefore, low in saturated clays, moderate in saturated sands/granular soils, and hi in dense rocks with a few voids, little moisture, and small amount of dissolved salts. 

Jackson, P.D. 1975. An electrical resistivity method for evaluating the in-situ porosity of clean marine sands. Marine Geotechnology, 1 2 91-115. 

ASTM G 96, Practice for On-Line Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)—This standard outlines procedures for online corrosion monitoring in operating systems. The test methods described in this standard are used to determine the cumulative metal loss (electrical resistance method) or instantaneous corrosion rates (electrochemical method). Reference 15 provides a summary of electrical resistance and polarization resistance theory. 

A. F. Tereshchenko. Investigation of the High-Temperature Characteristics of the Strength and Plasticity of Heat-Resistant Materials on Heating of Specimens by the Electrical Resistance Method, author s abstract of dissertation, Kiev, 1961. 

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