US Patent 7708939 Cooling water corrosion inhibition method

A method of providing corrosion inhibition to copper, nickel, aluminum, zinc, tin, lead, beryllium, carbon steel, various alloys of such metals, and galvanized coatings in evaporative cooling water applications approaching zero liquid discharge that are specifically attacked by cooling water with residuals of corrosive chemistry or ions such as ammonia/ammonium ion, chloride, high TDS, OH−, or high pH. The method includes applying azoles inhibitors (such as TTA, BTA, etc.) at residuals of 0.25 mg/L to 200 mg/L or greater (as azoles) to the cooling water application and operating with a combination of high TDS (greater than 2500 mg/L) and high pH (greater than 9.0), while maintaining low total hardness (less than 200 mg/L as CaCO3).