Inhibiting corrosion of iron base metals

• US 4,717,542 A
• Filed: 01/23/1987
• Issued: 01/05/1988
• Est. Priority Date: 01/23/1987
• Status: Expired due to Fees

• Current Assignee: W.R. Grace & Co.-Conn. (WR Grace & Company)
• Original Assignee: WR Grace & Company
• Inventors: Mitchell, Wayne A.
• Primary Examiner(s): THEXTON, MATTHEW
• Application Number:
  US07/006,393
• Time in Patent Office: 347 Days
• Field of Search: 252/389.23, 252/180, 210/699, 422/15, 422/13
• US Class Current: 422/15
• CPC Class Codes: C23F 11/10 using organic inhibitors

Abstract

A process and composition using hydroxyphosphonoacetic acid or its water-soluble salts in combination with certain copolymers, such as water-soluble 1-acrylamido-2-methylpropane sulfonic acid copolymers with acrylic acid or methacrylic acid, provide improved corrosion protection for iron based metal in contact with the system water of aqueous systems.

Claims

1. A composition suitable for inhibiting the corrosion of an iron based metal in contact with the system water in an aqueous system comprising a combination of

(a) hydroxyphosphonoacetic acid or a water-soluble salt thereof;

and in a weight ratio to component

(a) between about 10;

1 and about 1;

1000,

(b) a copolymer having the general formula;

##STR3## wherein R¹ and R² each independently represent hydrogen or methyl;

R³ represents hydrogen or C₁ -C₁₂ straight or branch chain alkyl group, or a cycloalkyl group having up to six carbon atoms or a phenyl group;

each M, which may be the same or different, represents hydrogen or an alkali metal cation or 1/2 an alkaline earth metal cation or an ammonium cation;

each Z, which may be the same or different, represents hydrogen or an alkali metal or ammonium cation;

x and y are integers such that the ratio of x to y is from 5;

1 to 1;

5 and the sum of x+y is such that the copolymer has a weight average molecular weight of 1,000 to 100,000.

2. A composition according to claim 1 wherein the water-soluble hydroxyphosphonoacetic acid compound is hydroxyphosphonoacetic acid, an ammonium salt thereof, or an alkali metal salt thereof.

3. A composition according to claim 2 wherein the copolymer is formed from 2-acrylamido-2-methylpropane sulfonic acid and acrylic acid or methacrylic acid, said copolymer-forming acids being in the form of free acids or at least partially neutralized with an alkali metal cation or an ammonium cation.

4. A composition according to claim 3 wherein the copolymer has a weight average molecular weight of from 1,000 to 10,000;

the ratio of x to y is from 2;

1 to 1;

2; and

the weight ratio of (a) to (b) is between about 20;

1 and 1;

5.

5. A composition according to claim 1 wherein R¹ is hydrogen, R² is methyl, R³ is hydrogen or a C₁ -C₃ alkyl and M is hydrogen, an alkali metal cation or an ammonium cation.

6. A composition according to claim 1 wherein the copolymer is formed from 2-acrylamido-2-methylpropane sulfonic acid and methacrylic acid.

7. A composition according to claim 1 wherein the copolymer has a weight average molecular weight of from about 4,000 to about 6,000;

the ratio of x to y is 2;

1 to 1;

2; and

the weight ratio of (a) to (b) is between about 5;

1 and 1;

1.

8. The composition of claim 7 wherein the copolymer is formed from 2-acrylamido-2-methylpropane sulfonic acid and methacrylic acid, or alkali metal or ammonium salts thereof;

and wherein the water-soluble hydroxyphosphonoacetic acid compound is hydroxyphosphonoacetic acid, an ammonium salt thereof, or an alkali metal salt thereof.

9. A process for inhibiting corrosion of an iron based metal in contact with the system water in an aqueous system comprising incorporating into the aqueous system an effective amount of a corrosion inhibiting mixture comprising

(a) hydroxyphosphonoacetic acid or a water-soluble salt thereof;

and, in a weight ratio to component

(a) between about 10;

1 and about 1;

1000,

(b) a copolymer having the general formula;

##STR4## wherein R¹ and R² each independently represent hydrogen or methyl;

R³ represents hydrogen or C₁ -C₁₂ straight or branch chain alkyl group, or a cycloalkyl group having up to six carbon atoms or a phenyl group;

each M, which may be the same or different, represents hydrogen or an alkali metal cation or 1/2 an alkaline earth metal cation or an ammonium cation;

each Z, which may be the same or different, represents hydrogen or an alkali metal or ammonium cation;

x and y are integers such that the ratio of x to y is from 5;

1 to 1;

5 and the sum of x+y is such that the copolymer has a weight average molecular weight of 1,000 to 100,000.

10. A process according to claim 9 wherein the water-soluble hydroxyphosphonoacetic acid compound is hydroxyphosphonoacetic acid, an ammonium salt thereof, or an alkali metal salt thereof.

11. A process according to claim 10 wherein the copolymer has a weight average molecular weight of from about 4,000 to about 6,000;

the ratio of x to y is from 2;

1 to 1;

2; and

the weight ratio of (a) to (b) is from about 20;

1 to about 1;

5.

12. A process according to claim 10 wherein R¹ is hydrogen, R² is methyl, R³ is hydrogen or a C₁ -C₃ alkyl and M is hydrogen, an alkali metal cation or an ammonium cation.

13. A process according to claim 9 wherein the aqueous system is a cooling water system.

14. A process according to claim 9 wherein the system water is substantially chromate-free.

15. A process according to claim 9 wherein the copolymer is formed from 2-acrylamido-2-methylpropane sulfonic acid and acrylic acid or methacrylic acid, said copolymer-forming acids being in the form of free acids or at least partially neutralized with an alkali metal cation or an ammonium cation.

16. A process according to claim 15 wherein the copolymer is formed from 2-acrylamido-2-methylpropane sulfonic acid and methacrylic acid.

17. A process according to claim 15 wherein the copolymer has a weight average molecular weight of from 1,000 to 10,000;

and the weight ratio of (a) to (b) is 20;

1 to 1;

1.

18. A process according to claim 17 wherein the system water is substantially chromate-free.

19. A process according to claim 18 wherein the copolymer has a molecular wieght of from about 4,000 to 6,000 and is formed from 2-acrylamido-2-methylpropane sulfonic acid and methacrylic acid, or alkali metal or ammonium salts thereof;

wherein the ratio of x to y is between about 2;

1 and 1;

2; and

wherein the hydroxyphosphonoacetic acid compound is hydroxyphosphonoacetic acid, an ammonium salt thereof, or an alkali metal salt thereof.

20. A process according to claim 19 wherein the aqueous system is a cooling water system.