Abstract
A polarisation resistance test which employs three identical sample probes and compensates for the inteiference of solution resistivity is described. The corrosion test vessel and probes. are treated as a conductivity cell for which the cell constant is found using a standard a-c bridge technique as a means of calculating the contribution of ohmic resistance (IR) to the polarisation resistance measurements. Data from two- and three-day exposures of mild steel and brass to salt and acid aqueous solutions yield an excellent linear correlation between corrosion rates predicted by the polarisation test and measurements of sample weight loss. The procedure offers a potential increase in precision over some other polarisation resistance tests, and the apparatus is fairly simple and can be made portable. The procedure is recommended for non-passive alloys and for industrial process waters where the corrosion rate is expected to be in the range 0·01–1·0 Am−2 and the solution resistivity is below 10,000 Ω cm
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