Apparatus for maintaining a stable bath for an autodeposition composition by periodically separating particular metal ions from the composition

A system automated for providing at least periodic removal of metal ions from a metal complex and contaminants from a chemical bath, said chemical bath being a latex solution containing charged latex particles and having an acidic pH to form a coating by autodeposition, said charged latex particles tending to coagulate when subjected to high shear circulation, said system comprising:

• a first tank containing said chemical bath;
• an ion exchange (IEX) column containing ion exchange material comprising an iminodiacetate ion exchange resin, for removing metal ion contaminants from said chemical bath;
• first circulation means responsive to first control signals for drawing chemical bath from said first tank, passing it through said IEX column at a low velocity, and returning treated chemical bath from said IEX column back to said first tank, said first circulation means including means for low shear circulation of said chemical bath to substantially prevent coagulation of said latex particles;
• first conductivity measurement means positioned in said chemical bath in said first tank, for providing a first conductivity signal indicative of the conductivity of said chemical bath;
• second conductivity measurement means immersed in said chemical bath being returned from treatment in said IEX column to said first tank, for providing a second conductivity signal indicative of the conductivity of treated chemical bath;
• and
• controller means programmed in a first state of operation for automatically initiating the production of said first control signals in a cyclic manner, and during the resultant circulation of said chemical bath, sensing the differential between said first and second conductivity signals reducing to a predetermined minimum value, for terminating said first control signals to turn off said first circulation means.