Patent ID: 7955553

Claim:
A method for inhibiting corrosion of a metallic substance in an aqueous system that is resistant to silica-based corrosion inhibition comprising the steps: a. providing source water to derive said aqueous system, said aqueous system containing greater than 2500 mg/L TDS and less than 200 mg/L CaCO 3 , ammonia and/or ammonium ions, and one or more substances selected from the group consisting of hydroxide ions, chloride ions and sulfate ions, wherein said ammonia and/or ammonium ions and said one or more substances are present in a concentration that is corrosive to said metallic substance; b. elevating and maintaining the pH of said aqueous system such that said aqueous system possesses a pH of approximately 9.0 or greater; c. adding at least one azoles inhibitor to said aqueous system at a total residual of at least 0.25 mg/L; and d. wherein said metallic substance is selected from the group consisting of copper, nickel, aluminum, zinc, tin, lead, beryllium, carbon steel, alloys of such metals, and galvanized coatings of such metals, and wherein said aqueous system includes a cathodic inhibitor film formed by an amorphous silica inhibitor, and the source water is selected from the group consisting of recycled waste water and municipal waste water.