Methods for inhibiting corrosion in aqueous media
View Patent ↗Methods are provided to inhibit corrosion of metals in contact with aqueous systems such as cooling water systems. In accordance with the methods, a hydroxyacid compound and orthophosphates are used to treat the system. Additionally, an adjuvant including poly(epoxysuccinic acids), an additional hydroxy acid, and a polycarboxylic acid, may be added to the system water.
1. In a water system having a total amount of from about 0.1-1.0 ppm of orthophosphate therein, an improved corrosion inhibition method comprising adding to said system an effective amount to inhibit metallurgy in contact with said water system of a hydroxy acid compound having the formula
Q′-(R 1) a —(R2) b —(R3) c —COOH
wherein a, b, and c are integers of from 0 to 6 with the proviso that (a+b+c>0); R1, R2, and R3 are repeat units in either random or block sequence and are individually chosen from C═O or CY′Z′ wherein Y′ and Z′ are individually selected from the group of H, OH, CHO, COOH, CH 3 , CH 2 OH, CH(OH) 2 , CH 2 (COOH), CH(OH)(COOH), CH 2 (CHO), and CH(OH)CHO so that said B(1) has a minimum of one OH group as written in its fully hydrated form, Q′ is COOH or CH 2 OH, said hydroxy acid being present in an amount of 1 to about 49 ppm said method further comprising adding a poly(epoxysuccinic) acid to said water system in an amount of about 1 to 40 ppm.
2. A method as recited in claim 1 wherein said water system is a recirculating cooling water system, said hydroxy acid being a member selected from the group consisting of D-saccharic acid, mucic acid, tartaric acid, ketomalonic acid, gluconic acid, and glucoheptonic acid.
3. A method as recited in claim 1 further comprising adding polymaleic acid to said water system in an amount of about 1 to 40 ppm.
4. A method as recited in claim 2 wherein said hydroxy acid is D-saccharic acid.
5. A method as recited in claim 4 wherein an additional hydroxy acid is present, said additional hydroxy acid being a member selected from the group of mucic acid, tartaric acid, ketomalonic acid, gluconic acid, and glucoheptonic acid.