Closed loop cooling water corrosion inhibition employing polymaleates and non-borate buffers

A method of inhibiting corrosion of a metal surface in contact with an aqueous medium, comprising:

• contacting the metal surface in a closed loop system with a corrosion inhibitor composition, wherein the corrosion inhibitor composition comprises an azole and a compound of formula (I), or a salt thereof,
• wherein
• L is a single bond or a double bond;
• R1 is
• n is an integer from 1 to 100;
• m is an integer from 1 to 100;
• p is an integer from 2 to 20;
• R3 is —OH, —OCH3, an aryl group, or a C1-C4 alkyl;
• R2 is hydrogen, —OH, —OCH3, an aryl group, or a C1-C4 alkyl;
• provided that when R1 is
• then L is a double bond;
• and
• adding the corrosion inhibitor composition to the aqueous medium, wherein the compound of formula (I) has a concentration of about 100 ppm to about 5,000 ppm in the aqueous medium, and the azole has a concentration of about 20 ppm to about 500 ppm in the aqueous medium, and wherein the corrosion inhibitor composition has a ratio of 5:1 to about 10:1 of the compound of formula (I) to the azole;
• wherein the azole is selected from the group consisting of tolytriazole (TT), benzotriazole (BZT), mercaptobenzothiazole (MBT), butyl benzotriazole (BBT), halogen resistant azole (HRA), a benzimidazole, and any combination thereof;
• and
• wherein the corrosion inhibitor composition does not comprise zinc and phosphorus.