Method of controlling solution concentration in strip cleaning line

摘要

An automatic control system is provided for acid concentration in an aluminum strip cleaning line wherein an aluminum strip is contacted with an acid solution while passing through an acid cleaning bath and the concentration of the acid in the bath is adjusted by adding either concentrated acid or water to the bath. A conductivity probe is provided in the acid bath and generates a first signal approximately proportional to the free acid concentration of the bath. An on-line process titrator periodically samples the acid bath and by a dual endpoint titration obtains the free acid concentration and total acid concentration of the bath and thereby generates a second signal indicative of the actual free acid concentration and the total acid concentration. These first and second signals are fed to a programmable logic controller, which based on the signal from the titrator calculates a correction factor for the signal from the conductivity probe to thereby obtain a corrected value for free acid concentration. The bath acid concentration is then adjusted as required based on the corrected specific conductivity value. The above procedure may also be used in the cleaning of an aluminum strip with an alkali solution.