GB1064485A - Corrosion rate measuring apparatus and method - Google Patents

Abstract

1, 064,485. Electro physical measurement control &c. PURE OIL CO. March 12, 1964, No.10553/64. Heading G1N . A method of determining the rate of corrosion of a material in an environment comprises disposing at least two pairs of differently spaced electrodes at least one of each pair of which comprises the material in the corrosive environment, supplying selectively a D. C. potential of known value and less than about 0.03 volts to one of the pairs of electrodes, measuring the I. R. drop across a resistor in series with the path between the electrodes, and using the supplied potential and I.R. drop to determine the corrosion rate. Electrode arrangements described as suitable and claimed independently comprise two ribbon like electrodes (244) (246), Fig. 14 (not shown), of the material to be tested, mounted on a base (220) and pleated at least once (248), (250); and a plurality of parallel plate or rod electrodes (10), (12), (14), (16) Fig. 1 (not shown) which are connectable to the measuring circuit through selector switches 26, 28 so that tests may be carried out for various plate spacings to eliminate electrolyte conductivity. Further electrode arrangements described include a pair of U-shaped tubular electrodes Fig. 16 (not shown) through which a temperature regulating fluid is caused to flow; a stack of ribbon like strips insulated one from the other and at the two ends by for example a polystyrene resin or polytetrafluoroethylene, the edges only of the ribbons being exposed to the environment, Figs. 16, 17 (not shown); a rod-electrode in combination with an electrode stressed by bending Fig. 13 (not shown), in which only the stressed part is exposed to the environment, and a dual arrangement Fig. 18 (not shown) of two compartments through which the flow of corrosive fluid may be controlled in accordance with its conductivity. In the measuring circuit Fig. 3 (not shown) after calibration with a variable 200 ohm resistor (58) the cell current is indicated by the position of a potentiometer wiper (69). A number of simple alternative measuring and recording circuits are described, and change over switches are provided for reversing the direction of the current. If the cell electrodes are dissimilar then the corrosion rate is indicated as the average rate for the two materials but if one of the metals is less active in the electromotive series e. g. steel in a cell comprising electrodes of steel and zinc, then the corrosion rate of the less active material can be determined.