Automatic ph control of chemical treating baths

Claim 1

A METHOD FOR CONTROLLING PH IN AN ACIDIC AQUEOUS CHROMATE COATING BATH IN WHICH THE ACIDITY CONTINUOUSLY DECREASES AS THE COATING OPERATION PROCEEDS, WHICH COMPRISES CONTINUOUSLY MEASURING THE ACIDITY AS PH OF THE BATH BY MEANS IMMERSED THEREIN, INTRODUCING REPLENISHING ACID TO THE BATH AT A POINT SPACED FROM THE POINT AT WHICH THE ACIDITY AS PH IS MEASURED, THE INTRODUCTION OF THE ACID IMMEDIATELY COMMENCING WHEN THE MEASURED PH ATTAINS A PREDETERMINED MAXIMUM UPPER VALUE NOT SUBSTANTIALLY GREATER THAN A PREDETERMINED OPTIMUM OPERATING VALUE AND THEREAFTER PROCEEDING AT A RATE SLOW ENOUGH TO ASSURE SUCH ABRUPT TERMINATING OF THE ACID FEED WHEN THE MEASURED PH IS REDUCED TO A PREDETERMINED MINIMUM LOWER VALUE NOT SUBSTANTIALLY LESS THAN SAID AFORESAID OPTIMUM VALUE WHEREBY THE ACID FEED IS PREVENTED FROM BEING EXCESSIVE AT ANY TIME TO OBJECTIONABLY INFLUENCE THE COATING BATH, AND AGITATING SAID BATH ADJACENT SAID POINT TO INTRODUCTION OF ACID TO THE BATH.

Claim 2

A METHOD FOR CONTROLLING PH IN AN ACIDIC AQUEOUS CHROMATE COATING BATH IN WHICH THE ACIDITY CONTINUOUSLY DECREASES AS THE COATING OPERATION PROCEEDS, WHICH COMPRISES CONTINUOUSLY MEASURING THE ACIDITY AS PH OF THE BATH BY MEANS IMMERSED THEREIN, INTRODUCING REPLENISHING ACID TO THE BATH AT A POINT SPACED FROM THE POINT AT WHICH THE ACIDITY AS PH IS MEASURED, THE INTRODUCTION OF THE ACID IMMEDIATELY COMMENCING WHEN THE MEASURED PH ATTAINS A PREDETERMINED MAXIMUM UPPER VALUE NOT SUBSTANTIALLY GREATER THAN A PREDETERMINED OPTIMUM OPERATING VALUE AND THEREAFTER PROCEEDING AT A RATE SLOW ENOUGH TO ASSURE SUCH ABRUPT TERMINATING OF THE ACID FEED WHEN THE MEASURED PH IS REDUCED TO A PREDETERMINED MINIMUM LOWER VALUE NOT SUBSTANTIALLY LESS THAN SAID AFORESAID OPTIMUM VALUE WHEREBY THE ACID FEED IS PREVENTED FROM BEING EXCESSIVE AT ANY TIME TO OBJECTIONABLY INFLUENCE THE COATING BATH, AND AGITATING SAID BATH ADJACENT SAID POINT TO INTRODUCTION OF ACID TO THE BATH.