NZ204711A

NZ204711A - Compositions for protecting metal surfaces against corrosion containing carboxylic acids

Info

Publication number: NZ204711A
Application number: NZ204711A
Authority: NZ
Inventors: J Rones; S Mollers; H Hoch; F Fischer
Original assignee: Occidental Chem Co
Priority date: 1982-06-26
Filing date: 1983-06-27
Publication date: 1986-02-21
Also published as: JPS5925977A; GB8317084D0; ZA834632B; GB2122598B; BR8303394A; AU561560B2; DE3223940A1; GB2122598A; AU1629583A; EP0099598A1; CA1219119A

Description

New Zealand Paient Spedficaiion for Paient Number £04711 20471 1 Priority Date(s): cSfci.

Complete Specification Filed: Class: ) J 2-1" FtB 1986 Publication Date: P.O. Journal, No: . • 0 IlltJIliSllflS & ti Bk V< • f.. i" T«^ ffJUNlss^] y P O NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION COMPOSITION FOR PROTECTING METAL SURFACES AGAINST CORROSION SUBSTITUTION OF APPLICANT UNDER SECTION 24 Oc.c_c<$ ^ w? c?i ( X/We, METALLGESELLSCHAFT A.G., a German company, of Reuterweg 14, Postfach 3724, D-6000 Frankfurt am Main 1, West Germany, hereby declare the invention for which i / we pray that a patent may be granted to brs/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page la) 2 04711 Ga-se—No-:—P—11 , l-gtH COMPOSITION FOR PROTECTING METAL SORFACES AGAINST CORROSION This invention relates to an improved composition for protecting metal surfaces against corrosion and, more particularly, relates to an 5 improved aqueous treating fluid for protecting metal surfaces against corrosion during contact with aqueous liquids and/or during.the storage of metal components after they have been treated with aqueous solutions, and to a concentrate composition for use in the 10 preparation of such aqueous treating fluid.

BACKGROUND OF THE INVENTION In order to protect metallic surfaces against corrosion when they are in contact with aqueous liquids or during storage after they have been treated 15 or contacted with aqueous liquids, it is customary to add anticorrosion additives to the water or other i . aqueous solution which is in contact with the metallic surfaces. Frequently, the anticorrosion additive system utilized must provide protection for several 20 different types of metals. For example, in recirculating heat exchanger systems or systems utilizing aqueous hydraulic fluids, and the like, the components of which the system is made may be of steel and/or cast iron, as well as aluminum, copper, brass, 25 zinc, or other metals or metal alloys, all of which must be protected against corrosion. In addition to the need to provide protection to a variety of different metals, the anticorrosion additives must be readily soluble and stable in water having various 30 degress of hardness and must not be adversely effected la 2047 1 by either high or low temperatures. Desirably, such anticorrosion additives are effective at relatively low concentrations and must not be toxic or irritate the skin or have an unpleasant odor. Finally, such additives should not present any significant waste disposal problems.

Over the years, numerous aqueous systems have been developed for the protection of specific, individual metals against corrosion. In the case of steel and grey cast iron, for example, alkaline solutions of nitrites, particularly sodium nitrite, have been used. Various organic substances have also been used to protect these materials, including benzoates, borates, soaps and- salts of amino acids or of sulfonamidocarboxylic acids, particularly the alkanolamine salts.

More specifically, European Patent specification 0,020,042 describes an anticorrosion agent which contains 5 - 20% by weight of an aliphatic monobasic acid of 8 - 20 carbon atoms, 0 - 4% by weight of a lubricant, 10 - 35% by weight of an aromatic mono-or polycarboxylic acid and an amine which forms a water-soluble salt with the aliphatic and aromatic acids. U.S. Patent 3,573,225 describes an anticorrosion agent which contains 50 - 100 parts of a salt of a saturated carboxylic acid of 6 - 18 carbon atoms with an amine of 6 - 12 carbon atoms, 20 - 200 parts of an alkali metal benzoate and 1-50 parts of an alkanolamide obtained as a reaction product from ethanolamine and a saturated fatty acid of 6 - 18 \" V c 204 7 U carbon atoms. Finally, U.S. patent No. 4 113,498 discloses an aqueous treatment fluid for protecting metal surfaces against corrosion which contains a reaction product of an aliphatic carboxylic 5. acid of 6 - 10 carbon atoms and a polyoxycarboxylic acid, such as gluconic acid or tartaric acid, with an alkanolamine. Although the foregoing, and other, systems have been found to be capable of reducing the corrosion of steel and cast iron, they have generally 10 not been found to provide adequate protection for other metals.

It has been found, for example, that virtually the only materials which will provide corrosion protection for aluminum are chromates or 15 silicates. In aqueous solutions, however, these materials are stable only at relatively high pH values and only in soft water. Similarly, with respect to zinc, in actual practice only chromates have been found to be useful for the prevention of corrosion. Although 20 U.S. Patent 4,093,780 discloses that esters of thioglycolic acid are suitable for preventing the formation of white rust on zinc, the poor water-solubility and strong, objectionable odor of these compounds has greatly limited their use. 25 Moreover, these materials have not been found to provide any significant corrosion protection for metals other than zinc.

In the case of copper and brass, anticorrosion agents based on mercaptobenzothiazole or 30 benzotriazole have been found to be particularly 3 2047 1 effective and are widely used. These materials, by themselves, have not been found to be effective anticorrosion agents for steel and, in many instances, when they are combined with materials which are effective in protecting steel against corrosion, there is a substantial decrease in the protection which they provide for copper and brass.

Actually, very little has been published in regard to the protection of mutli-metal systems. A review of this area is given by J. Webber entitled "The Inhibition of Corrosion in Industrial Cooling Systems", which appeared in Wirkstoff und Korrosion, Vol. 30 (1979), pages 713 - 722. According to this review, chromates are the only materials which provide significant corrosion protection for a number of different metals, including steel, cast iron, aluminum, copper, brass and zinc. Chromates, however, cannot be used in large amounts because of their toxicity and, recently, their use has been banned completely in many areas.

In addition to aqueous fluids for protecting metal surfaces against corrosion, oil emulsions have also been employed for protecting multi-metal systems. These, however, have many disadvantages which have severaly restricted their use. For example, the emulsions tend to separate in hard water and, as a concentrate, they are flammable. Additionally, the emulsions cannot be disposed of without going through expensive procedures to separate the oil portion from the aqueous portion. 204711 It is, therefore, an object of the present invention to provide an aqueous solution for protecting metal surfaces against corrosion both while the aqueous solution is in contact with the metal surface and during the storage of the metal components after they have been treated with the aqueous solution.

A further object of the present invention is to provide an improved aqueous solution which will protect a number of different metals against corrosion.

A still further object of the present invention is or provide a concentrate composition from which the improved aqueous anticorrosion solutions may be prepared.

These and other objects will become apparent to those of ordinary skill in the art from the description of the invention which follows.

SUMMARY OF THE INVENTION Pursuant to the above objects, the present invention is directed to an aqueous treating solution for protecting metal substrates against corrosion which comprises the salt of at least one aliphatic carboxylic acid containing 6-10 carbon atoms (component A), the salt of at least one poly hydroxycarboxylic acid having 6 - -8 carbon atoms (component B) , and the salt of at least one aromatic monocarboxylic acid (component C), wherein the salt-forming cations of components A, B and C are predominantly alkali metal ions and wherein the molar ratio of component A to component B is from about 10 : 1 to 1 : 5, the molar ratio of component A to component C is from about 5 : 1 to 1 : 5, and the molar ratio of component B to component C is from about 5 : 1 142. PATENT QFFSC# I 2 8 NOV 1985 ^ DECEIVED 2047 to 1 : 10. Surprisingly, it has been found that the foregoing combination of components in the aqueous treatment solution exhibit a synogistic effect in that significantly better corrosion protection results are obtained with this combination that are obtained using any one of the components along or in combination with only one further component. Further, it has been found that, contrary to conventional practice in which organic acid corrosion inhibitors are utilized in the form of the alkanolamine salts of the acid in the aqueous treating solutions of the present invention, the alkali metal salts of these organic acids are significantly more effective.

DETAILED DESCRIPTION OF THE INVENTION More specifically, in the practice of the present invention, the improved aqueous treating solution containing the components A, B and C, as have been described hereinabove, have a molar ratio of component A to component B of from about 10 : 1 to 1 : 5 and, preferably, from about 4 : 1 to 1 : 2. The molar ratio of component A to component C is from about 5 : 1 to 1 : 5 and, preferebly, from about 2 : 1 to 1 : 2. The molar ratio of component B to component C is from about 5 : 1 to 1 : 10 and, preferably, from about 2 : 1 to 1 : 4.

The concentrations of the A, B and C components in the aqueous treating solutions of the present invention may be varied over a relatively wide range, depending upon the manner in which the composition is utilized and the particular metal 6 204713 substrates which are to be protected against corrosion. Typically, the three components A, B and C are present in the aqueous treating solution in a total amount of from about 0.2 to about 4.0% by weight of the aqueous treating solution. Preferably, these components are present in a total amount of about 0.5 to about 2.0% by weight of the aqueous treating solution. It will be appreciated, however, that other amounts of these components may also be used and still obtain advantageous corrosion protection results.

As has been set forth hereinabove, component A is made up of the salt of at least one aliphatic carboxylic acid having 6-10 carbon atoms.

Particularly preferred compounds of this class are the salts of caprylic acid and/or ethylhexanoic acid. Component B is made up of the salt of at least one polyhydroxycarboxylie acid having 6-8 carbon atoms. Particularly preferred compounds of this class are the salts of gluconic acid and/or heptonic acid. Component C is made up of the salt of at least one aromatic monocarboxylic acid. A particularly preferred compound of this class is the salt of benzoic acid.

The salt-forming cations of these acid components are predominantly alkali metal ions. Additionally, however, at least some of such salt-forming cations may also be ammonium ions. In this latter instance, however, it has been found that optimum corrosion protection results are achieved where the content of ammonium ions in the aqueous treating solution is not substantially in excess of about 20% of ;PAT5wr0pncj 2 8 NOV 1985 nSCEIVED 2047 the total cation content. Additionally, it is to be appreciated that although excellent corrosion protection results are obtained when the components A, B and C are formed of only one of the acid salts of the 5 defined classes, in some instances it may be preferable to form one or more of the components of a combination • of two or more of the acid salts of the class defined.

In addition to the A, B and C components which have been described hereinabove, the aqueous 10 treating solutions of the present invention may also contain one or more non-ionic surfactants, preferably those having a turbidity point below about 30°C. Such surfactants are water-soluble at low temperatures.

When the turbidity point of Hfie surfactants is reached, 15 the solutions begin to become cloudy and the foaming action of the surfactant solution is noticeably reduced. It has been found that by the addition of these non-ionic surfactants, the wetting of the metal surfaces is improved so that the treatment solutions 20 are able to act even on moderately greasy or dirty metal substrates. Non-ionic surfactants which have .been found to be particularly useful are the polyglycol ethers of fatty alcohols, fatty amines and polyamines, and polglycol esters of fatty acids, which have been 25 reacted with ethyleneoxide and propyleneoxide.

Particularly advantageous surfactants of this type are the high molecular weight block polymers of polypropyleneglycol condensed with ethyleneoxide and the high molecular weight block polymers of 30 polyethyleneglycol condensed with propyleneoxide. 8 / Surfactants of this type are sold under the designation Pluronic 62 by Wyandotte, U.S.A. Although various amounts of such surfactant may be used in the aqueous treating solutions of the present inventions, they are 5 typically present in amounts from about 0.003 to about 0.5% by weight of the total solution, with amounts within the range of about 0.01 to about 0.35% by weight being particularly preferred.

The aqueous treating solutions of the 10 present invention may also contain one or more additional conventional corrosion inhibitors for individual metals, provided such additional corrosion inhibitors are compatible with the other components in the treating solutions and d©?not have an adverse 15 effect on the corrosion protection of any of the metal substrates which are contacted by the solution.

Typical of such other corrosion inhibitors which may be used are boric acid esters, salts of higher carboxylic acids, salts of amino acids, salts of 20 sulfonomidocarboxylic acids and fatty acid alkanolamides. Where the treating solutions will be in contact with copper and/or brass components, the solutions may also advantageously contain mercaptobenzothiazoles, ben?otriazole and their 25 derivatives. Finally, the aqueous treating solutions of the present invention may also contain further additives to prevent or at least minimize attack on the solution and/or the treated metal substrates by microorganisms. Typically, such additives may include 30 biocides, such as phenol derivatives, formaldehyde or 9 2047 I compounds which will evolve formaldehyde, triazines, quarternary ammonium compounds, and the like.

The total aqueous treating solutions will typically have a pH within the range of about 7 to 10 and, preferably, will have a pH within the range of about 8 to 9. The salts of the various organic acids or components A, B and C which are used in the present solutions may be simply prepared by mixing the organic acid with the appropriate alkali and water at temperatures of about 40 - 90°C.

While the aqueous treating solutions may be prepared from solid salt mixtures, they are preferably formulated using a liquid concentrate which can be very easily diluted with water to"form the final treating solution containing the components in the desired concentrations. Such concentrate componsitions, which form a part of the present invention, will typically contain the components A, B and C in solution in water, in a total concentration of about 30 - 80% by weight. Where a surfactant as described above is also included in the composition, such surfactant may be a part of the concentrate and is typically present in an amount within the range of about 0.5 to 10% by weight of the concentrate, preferably from about 1 to about 4% by weight.

By the use of the aqueous treating solutions of the present invention, exceptional anticorrosion results are obtained on a wide variety of metal substrates. These solutions are found to provide corrosion protection for these metal substrates while 2047 they are in contact with the solution. Additionally, corrosion protection is provided against residual water which may remain on the metal surfaces after they have been removed from the treating solutions.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. In these examples, Examples 9 through 11 are examples of the compositions of the present invention. Examples 1 through 8 and 12 are examples of solutions containing one or more of the individual components of Examples 9 through 11 but less than all of these components, or of compositions made up of salts other than the alkali metal salts.

In testing the various solutions of Examples 1 through 12, test sheets having the dimensions 100 x 20 x 1 millimeters of steel, aluminum, copper, brass (70/30 copper/zinc) and zinc were weighed. These test sheets were then half-submerged in water of 22.4°dH (adjusted by means of clacium chloride additions) both with an without the addition of various corrosion inhibitor compositions. The test sheets were maintained half-submerged in the various solutions in beakers, covered with a watch glass, for 28 days at a temperature of 35°C. Thereafter, the test sheets were removed from the solutions, rinsed and dried and again weighed. The inhibitory value of the various corrosion inhibitor additives was determined in accordance with the following formula: 2 047 I 1 (M! - M2) * 100 wherein M-| equals the loss in weight in water without an additive and M2 equals the loss in weight in the inhibited solution. The various solutions tested and the inhibitory values obtained are as follows: 12 am No 1 2 3 4 6 7 8 9 11 12 20471 I - 0 0 0 0 0 40 0 0 70 0 0 0 0 0 Concentration Inhibitory Values Composition g/L Fe A1 Zn Cu Brass Water 22.4°dH Na caprylate Na gluconate Na benzoate Block polymer of polypropylene glycol with ethylene oxide (Plur-onic 62 from Wynadotte U.S.A. """? Na caprylate 9 30 40 20 20 20 Na gluconate 6 Na caprylate 8 80 60 30 20 20 Na benzoate 7 Na caprylate 6 90 85 85 40 40 Na gluconate 4 Na benzoate 5 As for Example No. 90 90 90 40 40 9 + Pluronic 62 2 As for Example No. 90 90 90 99 99 + benzotriazole 1 as for Example No. - 95 70 70 80 80 11, but triethanol-amine salts 13

Claims

2047 While the above disclosure sets forth and describes various embodiments of the present invention, the compositions described are intended to illustrate but not limit the present invention. It will be 5 understood that the specific embodiments described herein are subject to variation and modification by one skilled in the art having the benefit of the present disclosure and it is, therefore, intended that the present invention is to be limited solely by the 10 following claims. 14 204711 .WHATvf/V.'H CLAi.M ifi; W«A3^S-eEATtteEr^S^- 1 1 . A composition for protecting metal 2 surfaces against corrosion which comprises an aqueous 3 solution comprising the salt of at least one aliphatic 4 carboxylic acid having 6 to 10 carbon atoms (component 5 A), the salt of at least one polyhydroxycarboxylic acid having 6 6 to 8 carbon atoms (component B) and the salt of at 7 least one aromatic monocarboxylic acid (component C), 8 wherein the salt-forming cations of the acids of said 9 components A, B and C are predominantly alkali metal 10 ions and wherein the molar ratio of component A to 11 component B is from 10 : 1 to 1 : 5, the molar 12 ratio of component A to component C is from 5:1

1.3 to 1 : 5 and the molar ratio of component B to 14 component C is from 5 : 1 to 1 : 10. 1 2. The composition as claimed in Claim 1 2 wherein the molar ratio of component A to component B 3 is from 4 : 1 to 1 : 2, the molar ratio of 4 component A to component C is from 2 : 1 to 1 : 2 5 and the molar ratio of component B to component C is 6 from 2 : 1 to 1 : 4. 1 3. The composition as claimed in Claim 1 2 wherein the components A, B and C are present in the 3 composition in a total amount of from 0.2 to 4% 4 by weight of the composition. 15 2 8 NOV 1985 JVED 1 2 3 4 1 2 3 4 5 1 2 3 1 2 3 4 1 2 3 4 1 2 3 4 1

2

3 4 5 6 7 204711

4. The composition as claimed in Claim 2 wherein the components A, B and C are present in the composition in a total amount of from 0.5 to 2% by weight of the composition.

5. The composition as claimed in Claim 1 wherein component A is selected from the salts of caprylic acid and ethylhexanoic acid, component B is selected from the salts of gluconic acid and heptonic- -acid, and component C is the salt of benzoic acid.

6. The composition as claimed in Claim 1 wherein there is also contained at least one non-ionic surfactant having a turbidity point below 30°C.

7. The composition as claimed in Claim 6 wherein the surfactant is selected from block polymers of polypropylene glycol with ethylene oxide and block polymers of polyethylene glycol with propylene oxide.

8. The composition as claimed in Claim 6 wherein the surfactant is present in the composition in an amount within the range of —: 0.003 to 0.5% by weight of the composition.

9. The composition as claimed in Claim 8 wherein the surfactant is present in the composition in an amount within the range of 0.01 to 0.3% by weight of the composition.

10. The composition as claimed in Claim 6 wherein there is also present at least one additional corrosion inhibitor selected from boric acid esters, salts of higher carboxylic acids, salts of amino acids, salts of sulfonamidocarboxylic acids, salts of fatty acid alkanolamides, mercapto benzothiazole, and benzothiazole. * 2 8 NOV 1985 RECEIVED / 16 1 2 3 1 2 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 2 3 4 5 6 204711

11. The composition as claimed in Claim 10 wherein the solution has a pH within the range of 7 to 10.

12. The composition as claimed in Claim 11 wherein the solution has a pH within the range of 8 to 9.

13. An aqueous concentrate composition, suitable for the preparation of aqueous treating solutions for the protection of metal surfaces against corrosion, which concentrate comprises the salt of at least one aliphatic carboxylic acid having 6 to 10 carbon atoms (component A), the salt of at least one polyhydroxycarboxylic acid having. 6 to 8 carbon atoms (component B) , and the salt of at least one aromatic monocarboxylic acid (component C), wherein the salt-forming cations of the component A, B and C acids are predominantly alkali metal ions, and wherein the molar ratio of component A to component B is from 10 : 1 to 1 : 5, the molar ratio of component A to component C is from 5 : 1 to 1 : 5 and the molar ratio of component B to component C is from 5:1 to 1 : 10 and the components A, B and C are present in a total amount of from 30 to 80% by weight of the aqueous composition.

14. The concentrate composition as claimed in Claim 13 wherein there is also present at least one non-ionic surfactant having a turbidity point below 30°C, which surfactant is present in the concentrate composition in an amount of from 0.5 to 10% by weight of the composition. 17 ' 2 8 NOV 1985 fffiCESV* « * 204711 1

15. The concentrate composition as claimed 2 in Claim 14 wherein the surfactant is selected from 3 block polymers of polypropylene glycol with ethylene 4 oxide and block polymers of polyethylene glycol with 5 propylene oxide. 1

16. The concentrate composition as claimed 2 in Claim 15 wherein the surfactant is present in an 3 amount of from 1 to 4% by weight of the aqueous 4 concentrate composition.

17. An aqueous concentrate composition suitable for the preparation of aqueous treating solutions for the protection of metal surfaces against corrosion substantially as herein described with reference to Examples S to 11. Qcjc-i <A ic exA wch Byjite/Thair Authorisod Agents, A. J. PARK & SON Per 18 2 8 NOV 1985 aSCSVBD