US 3705786 A
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United States Patent O) CORROSION INHIBITION WITH METHYLENE BIS-BENZOIC ACID Saul Kaye, Evanston, Ill., assignor to Ventron Corporation, Beverly, Mass. No Drawing. Filed Nov. 23, 1970, Ser. No. 92,174 Int. Cl. C23f 11/12 U.S. Cl. 212.7 4 Claims ABSTRACT OF THE DISCLOSURE This application is directed to corrosion inhibition of ferrous materials in an aqueous environment by employing 3,3'-methylene bis-benzoic acid.
BACKGROUND OF THE INVENTION A number of materials are conventionally employed to inhibit corrosion particularly with respect to ferrous materials, e.g., steel. Such materials include inorganic compounds such as phosphates, chromates, nitrates, etc., organic compounds such as triethylamine, propylenediamine, picoline, tertiary butyl phenol, diphenylthiourea, lignin sulfonates, and surface active agents such as the anionic surfactants, e.g., alkyl aryl sulfonates, sodium N-methyl N-acyl taurates, etc., the anionic surfactants, e.g., fatty acid esters of higher polyglycols, ethylene oxide condensates, and the cationic surfactants, e.g., lauryl dimethylbenzyldimethyl ammonium chloride, etc.
However, such inhibitors are deficient in some respect, i.e., with regard to effectiveness, compatability with additives or other components of the system sustained effectiveness, and the like. A deficiency of particular importance is the effect on the ecology When such materials are discharged from the system in which they are functioning, particularly the accelerated growth of algae resulting from contact with phosphates. Chromates and phenols are also preferably avoided as corrosion inhibitors because of the undesirable effects on ecology.
A corrosion inhibitor has now been found which is not susceptible to the deficiencies of the prior art.
SUMMARY OF THE INVENTION The present invention is directed to the employment of the compound:
COOH COOH 3,3'-methylene bis-benzoic acid in an aqueous environment in contact with ferrous materials. In a particularly preferred embodiment, the indicated compound is employed in a recirculating water system, i.e., both heating and cooling systems. The above-indicated compound is preferably added to the system as an alkali metal or ammonium salt.
In addition to being a highly efficient corrosion inhibitor, thus significantly lengthening the life of the equipment, 3,3'-methylene bis-benzoic acid is not detrimental to the ecology, i.e., will not deleteriously interfere with plant or animal life if discharged into streams.
DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the employment of 3,3-methylene bis-benzoic acid in an aqueous environment as a corrosion inhibitor. As stated above, the compound is preferably added to the system as an alkali metal or ammonium salt.
The level of inhibitor employed is not critical; the particular level employed is determined at the option of the operator depending upon the degree of protection desired, the severity of the operating conditions, etc. A range of 60 to 150 ppm. in water, preferably ppm. is generally employed. It should be understood, that if desired, levels ,in excess of ppm. or less than 60 p.p.m. may be utilized in a given system.
The preparation of 3,3'-methylene bis-benzoic acid is known to the art. For example, the method set forth in U.S. Pat. No. 3,113,148 or Berichte 27, II, pp. 2321-2326, may be employed.
The following nonlimiting example illustrates the prep aration of 3,3'-methylene bis-benzoic acid.
Example I The compound was prepared by the method of Schopff (Berichte 27, II, pp. 2321-2326, May-July 1894). Two hundred and fifty grams (2 moles) of benzoic acid were dissolved in 1500 grams concentrated sulfuric acid contained in a 2 liter flask. The flask was set in an ice-bath and the temperature (which rose due to heat of solution) was allowed to drop to 20 C.; 110 ml. of 37% formaldehyde solution (1.2 moles HCHO) were introduced slowly with stirring and swirling. After the heat and fumes had dissipated, the flask was stoppered and allowed to stand for 5 days; at the end of this time, the liquid was brown and had no odor of formaldehyde. The flask contents were poured into a mixture of 1500 ml. water and 1500 grams of ice and the crude yellow product which precipitated was filtered off on a Buchner funnel. This crude material was washed several times with cold water, then 250 ml. ammonia and 1500 ml. of water were added to dissolve it. The resulting green solution was treated with 3 grams of activated carbon and filtered, then the acid reprecipitated with 50% sulfuric acid, and cooled. The precipitate was filtered on a Buchner funnel, washed with cold water, and then the mass was broken up in a large beaker and stirred thoroughly with hot (70 C.) water. The material was filtered again and further washed on the funnel with hot water (a total of 5 liters of hot water was used). The product was dried in a vacuum oven at 50 C. overnight. No sharp melting point was found; sintering occurred between and 200 C., melting from 220-230 C.
The effectiveness of 3,3'-methylene bis-benzoic acid as a corrosion inhibitor was determined by the following procedure.
Sheets of mild cold rolled steel 0.036 inch thick were cut into strips /2 inch wide and 2 inches long, and were wire-brushed, degreased, cleaned in 10% hydrochloric acid, rinsed with distilled water and then with acetone, dried, and stored in a dessicator until ready for use.
Two such coupons were immersed in 100 ml. of tap water containing the corrosion inhibitor in dissolved form, Whose pH had been adjusted to 6-8. The test solutions were contained in test tubes 38 mm. in diameter and 200 mm. long which were held in a water bath maintained at 50 C.-* -l C. Each test tube contained a twoholed rubber stopper, one hole of which contained a glass tube 3 mm. in inside diameter, which reached to the bottom of the test tube. The narrow glass tubing was used to aerate the water; laboratory compressed air was passed through a flask containing water, for humidification, and thence through the test solutions. Test usually lasted 5 days, during which time the air passed through the test tubes for 16 hours of each 24; for the remaining 8 hours, no air was admitted.
At the end of the exposure period, coupons were removed, rubbed free of deposit, cleaned by exposure to 10% HCl for 30 seconds, rinsed, scrubbed with a nylon brush, wiped dry, wiped with acetone, dried, and weighed. In every test all coupons were the same size, and control. solutions containing only tap water were used as un- 75 TABLE Corrosion, as percent of unprotected coupon 3,3-methyl- P.p.m. of compound Benzoic ene bis-benin solution 1 acid zolc acid From the above table, it complete corrosion inhibition is achieved at a relatively low level with the corrosion inhibitor of the present invention. That relatively large quantities of a related compound are required to even approach the effectiveness achieved by the compound of the present invention at a low level, indicates the unobviousness of the present invention.
The novel inhibitor of the present invention may be employed in any aqueous environment where corrosion of ferrous metal in the system is a problem. Such systems include, but are not limited to, recirculating water systems, tanks, pipelines, radiators, and other aqueous based can be seen that virtually ferrous metal contacting systems. It has also been found unexpectedly that superior corrosion inhibitor characteristics can be achieved by adding to creosote compositions 3,3-methylene bis-benzoicacid at a level ranging from 0.05 to 1%, preferably 0.1% by weight, based on the weight of the creosote composition. The employment of such creosote compounds in the conventional manner results in minimization or elimination of corrosion generally encountered in such situations, when the creosote also contains pentachlorophenol as an adjuvant to its protective action.
1. The method of inhibiting corrosion of ferrous metal materials which comprises contacting said metal in an aqueous environment with an effective amount of 3,3- methylene bis-benzoic acid.
2. The method as defined in claim 1 wherein said ferrous metal is steel.
3. The method of inhibiting corrosion of ferrous metal materials which comprises contacting said metal with methylene bis-benzoic acid in an aqueous solution at a level ranging from to 150 ppm.
4. The method as defined in claim 3 wherein said 3,3- methylene bis-benzoic acid is employed at a level of ppm.
References Cited UNITED STATES PATENTS 3,113,14'8 12/1963 Le Blane et a1. 260-515 P LEON D. ROSDOL, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R.