Controlled process for the surface treatment of metals

Abstract

A control system for the surface treatment of metals in a bath open to the atmosphere, containing an organic solvent and reactive component, and being superimposed by a cold cushion of air forming a condensate of solvent and condensed humidity, comprising passing resultant condensate to a phase separator to separate an organic phase from an aqueous phase, said aqueous phase containing both solvent and reactive component, rcycling said organic phase to the treatment tank, passing the aqueous phase from the phase separator to an overflow tank; dosing a readjustment solution to said bath to make up for losses of components therein; adjusting the components, except for water, in the readjustment solution to obtain the same proportion of the same components in the overflow tank, the water in said readjustment solution being adjusted to have a lower concentration than the water concentration in said overflow tank and a sufficiently high concentration to avoid localized concentrations of the reactive components in the bath, and withdrawing from said overflow tank sufficient aqueous phase to maintain a constant volume of liquid in the treatment tank, a pumping arrangement of mechanically coupled or synchronous pumps being used for the dosing of the readjustment solution and the withdrawal of the aqueous phase.