Apparatus for monitoring the corrosion rate of metal by the polarization resistance method

Abstract

Abstract An apparatus for monitoring the corrosion rate of meatal in a plant stream by its polarization resistance featuring automatic means to reduce current flow through a metal specimen electrode before subjecting it to programmed polarization potentials. Spurious signals due to circuit oscillation are limited by using a current-to-voltage transducer that introduces essentially zero impedance in the current circuit to produce a functional voltage proportional to specimen electrode current. The functional voltage indicates corrosion rate by meter and alarm, and is inverted and amplified at moderate gain to provide and automatic current reduction signal through an isolating sample-and hold circuit. By a timing sequence the summing point of an operational amplifier receives both an input proportional to the inverted and amplified functional voltage and a continuously transmitted reference voltage from a freely corroding reference electrode during a fist time period. Additional programmed polarization voltages are introduced for summing during a second time period to establish polarization resistance. Circuit stability resulting form the use of low impedance components and restricted transmission of oscillations between circuit loops permits reliable monitoring of the corrosion of a wide variety of troublesome passive metals that form thin oxide films of high electrical capacity.

Inventors

• 👤 J Frenck

Bibliographic Details