Uited States Patent Q 3,573,225 RUST-PROOFING COMPOSITE SOLUTIONS Masahiko Kondo, 3-14-7 Maechi, Saitama Prefecture, Urawa, Japan, and Tetsuo Shinmura, 27 Futaba-cho, Itabashi-ku, Tokyo, Japan No Drawing. Filed Feb. 1, 1968, Ser. No. 702,209 Int. Cl. C23f 11/14, 11/10 US. Cl. 252-392 6 Claims ABSTRACT OF THE DISCLOSURE Rust-proofing aqueous or alcoholic composite solutions for application to metal surfaces consisting essentially of an amine salt of a fatty acid, an alkali metal salt of ben- Zoic acid and an alkanolamide.
This invention relates generally to rust-proofing compositions for application to metal surfaces and has particular reference to such aqueous or alcoholic composit solutions which consist essentially of an amine salt of a fatty acid, an alkali metal salt of benzoic acid and an alkanolamide.
There are known a variety of rust preventives useful for protecting metal surfaces against corrosion attack, most widely used of which is an oil-film forming material. This material also varies in kind, and although some are better than the others in terms of the length of time in which they retain rust-proofing efficacy, they are all adequate for all practical purposes.
However, these unctuous rust preventives are difficult to remove from the metal surfaces to which they have been applied. This film removal operation is time-consuming and troublesome, requiring the use of an alkali solution or chlorinated solvents such as trichloroethylene and perchloroethylene with which to wash the film otf sometimes with heating, or sometimes using petroleum series solvents.
To eliminate such difficulty, there have more recently been introduced certain water-soluble rust-proofing com positions which need not be removed after deposit on the metal surfaces or may be removed with ease. Typical examples are an alkali metal nitrite, dicyclohexylammonium nitrite, cyclohexylammonium nitrite and an alkali metal chromate. These aqueous solutions have been found useful insofar as the metal is soaked therein, but they are not quite as effective as oil counterparts when applied to the metal surfaces and exposed to the outside atmosphere for extended periods of time.
It is the primary object of the present invention to provide new, useful rust-proofing or rust-preventive compositions of this character which have prolonged efficacy in protecting metal surfaces against corrosion and which can be removed therefrom with utmost ease as the occasion calls for.
It is another object of the invention to provide rustproofing compositions which, on application to metal surfaces, will form a transparent or translucent uniform film thereby retaining the original surface appearance of the metal.
.Briefiy stated, the inventive concept of the present invention resides in the peculiar combination of an amine salt of a fatty acid, an alkali metal benzoate and an alkanolamide whereby there is obtained a highly effective, long-lasting rust preventive product. It has been empirically ascertained that the absence of any one of the three compounds or any one thereof alone cannot achieve the desired characteristics of the rust preventives comparable to, or better than existing oil type counterparts.
An amine salt of a fatty acid having a certain range of molecular weight is known as a volatile rust preventive 3,573,225 Patented Mar. 30, 1971 compound which tends to sublimate at room temperature.
An alkali metal benzoate is known as a contact rust preventive compound useful for coating on metal surfaces, and it may be added with a corrosive solution to make the most of its rust-preventive tendency.
An alkanolamide has both surface-active and contact rust-preventive properties. This surface-active agent helps reduce the surface tension of the composite solution when applied to metal surfaces, so that the contact rust-preventive tendency of the solution is so much increased.
It has been discovered that an amine salt of a fatty acid, e.g. cyclohexylamine laurate, and an alkali metal bonzoate, e.g. sodium benzoate, are highly conducive to the rust-preventive life time, while an alkanolamide co-present in the composite solution serves to reduce the surface tension thereof, so as to facilitate its deposit on metal surfaces. Experiments show that the rust-proofing composite solution according to the invention will form on the metal surface a uniform film about 0.005 to 5 microns thick after the water or alcoholic contents thereof have evaporated.
There are different theories to account for the mechanism in which organic corrosion-inhibitors exhibit their rust-proofing activity on metal surfaces. One theory is based on the physical adsorption of the inhibitor to the metal surface. Another theory is based on the chemical adsorption. Still another theory attributes it to the formation of a chelate compound.
With an organic corrosion-inhibitor dissolved in water, alcohol or benzene, for application to metal surfaces, it would be useless, were it not for a deposit of adequate amounts of the inhibitor on the metal surfaces, even if there has been formed a chelate compound which would necessarily be only appreciable and susceptible to destruction by ambient causes.
On the other hand the alkanolamide included in the composite rust-preventive composition according to the present invention has a peculiar surface-active effect to permit the amine salt of a fatty acid and the alkali metal benzoate to deposit on metal surfaces in an amount greater than required for chemical adsorption, although it does not possess as great corrosion-inhibitive activity as the latter two compounds.
Experiments revealed that the best results are obtainable by blending 50l00 parts by weight of amine salt of fatty acid, 20-200 parts of alkali metal benzoate, and 1-50 parts of alkanolamide to 0.520% consistency in an aqueous or alcoholic solution. Blends in excess of the upper limit of this range were found commercially unfeasible, and those less than the lower limit inoperative. More specific blending proportions will be discussed in the examples given hereinafter.
The term, amine salt of fatty acid according to the invention includes reaction products of a saturated fatty acid having a carbon number of 618 with an alkylor cycloalkyl-amine having a carbon number of 6-12, for example, cyclohexylamine laurate, dicyclohexylamine caprylate, cyclohexylamine myristate and octylamine stearate. The saturated fatty acid and the amine are reacted in a mol ratio equivalent to each other, or with a slight excess of the latter, the resulting product being in the form of a salt free of amide bonds.
The term alkali metal benzoate includes sodium benzoate, potassium benzoate and lithium benzoate. Instead of the alkali metal benzoate, nitrite compounds such as sodium nitrite may be used.
The term alkanolamide includes reaction products of a fatty acid having a carbon number of 618 with N-hydroxyethyl or N,Nbis-hydroxyethyl capramide, N-hydroxyethyl or N,N-bis-l1ydroxyethyl oleamide; or N-hydroxyethyl or N,N-bis-hydroxyethyl lauramide. 1 mol of such fatty acid is reacted with 2 mols of the alkanolamide, so that the excess of the latter loosely combines with the resulting amide thereby affording enhanced water-solubility.
The rust-preventive compositions according to the invention may be applied to iron, alloys thereof, alumi- 4 purposes of comparison. Each packed test piece was placed in a 60 C., 90% relative humidity constant temperature container and disposed thus for 15 consecutive days, with the results given in Table l.
5 num, tin, zinc, and other metals. This may be done by the EXAMPLE 2 use of brush, rolls, sprayers, or otherwise by dipping the metal in the composite of the invention. Three gltlerent sample solutlon? prepared a manner similar to Example 1, using d1cyclohexylam1ne EXAMPLE 1 caprylate, N-hydroxyethyl oleamide and sodium benzoate. There were prepared three difierent aqueous solutions: Water methanol were used as scilvelltkThe samitest the first was a composite aqueous solution of cyclohexylm Extmple 1 was treatFd m 3 cmdltlons amine laurate N,N bis hydmxyethyl lauramide} and to1 0 tam onh 1ts surface 0 6 micron thlck film of the sodium benzoate; the second was a composite aqueous Eac Packed test Plece 0 dlsposefl for days solution of any two of the above three compounds; and 15 m q fi temperatllvre col'llallief Cychng every 16 the third was a mono aqueous solution of any one of the 2 2 l 2 of E 60 and 80% l f above three compounds, as tabulated below um it an every ours with another set of cond1t1ons of 5 C. and 80% relative humidity. Commercially available oil-type counterparts similarly participated in this 20 test. Test results are shown in Table 2. I
TABLE 1 Corrosioninhibitive TABLE 2 Amounts factor Compounds by weight (percent) Corrosion- Arnounts inhibitive 1( DIyIsIIcaliezrglilimine laurlalte "a... 10% C d lily factorisy roxyet 1y aurami e. 1 ompoun s Wei 1; ercent) Sample Sodium benzoate. 100 100 g p Water 1. 3,000 Dieyclohexylamlne caprylate- 100 Cyclohexylamine laurat 150 N-hydroxyethyl oleamide... 20 N,N-bis-hydroxyethyl laura 60 75 581111310 Sodium benzoate 100 100 Water a, 000 1,500 S 1 Cyclohe aur 150 1,500 amp 9 Sodium heuzoate 60 90 200 ater 3,000 N-hydroxyethyl oleamide 20 N ,N-bis-hydroxycthyl laurarm e.. 150 Water 1,500 Sodium benzoata 60 9 sample 2 Methanol 1, 500 Water 3,000 Dicyclohexylamine eapry1ate 110 Cyclohexylarninelaura e 210 so Sodlum benzoate 110 85 Water. "Kart i 3, 000 xlgtitgnnl 1, 580 N,N-bisoxyethyl auranu e 210 1 6 am 1,5 0 Sample \vateruui 3,000 i 70 Dicyclohexylamine enprylate. 220
Sodium benzoate 210 85 Water 1,500 60 Water 3, 000 Methan 1, 500 Conventional oil type rust preventives 95 s 1 3 N-hydroxyethyl o1eamlde 220 Untreated steal 20 40 amp 6 Water 1,500 40 Methanol- 1, 500 Note.Corrosi0n-inhibitive factor is represented by rust-free surface S0d1l1mbe11Z0flt6- 220 area/test piece surface area X 100. Water 1, 500 75 Methan 1,500 Conventional oil type rust preventives. 80 Untreated steel 5 NoTn-Corrosionduhibitiye factor is represented by rust- A test piece of cold-roll steel measuring mm. x free Surface e e p e s face a ea x100. mm. X 1.2 mm. was immersed in each sample solution and immediately taken out for exposure to the atmosphere EXAMPLE 3 for about 30 minutes, until a film of this solution about 0.7 micron thick was formed on the surfaces of the test 50 Example 2 was followed, except for the use of pure piece. The test piece thus treated was packed in a. polyaluminum measuring 60 mm, x 8 mm. x 2 mm. as a test ethylene laminated paper but unsealed to permit aeration. piece. Corrosion of the test piece was determined by Commercially available rust preventives of the oil type comparing the surface condition of the test piece prior also participated in this test under similar conditions, for to treatment with that after treatment.
TABLE 3 Amounts Y Compounds weight Surface condition Dicyclohexylamlne eapry1ate N-hydroxyethyl eloamide 20 sample Sodium benzoate 100 Unchanged. Water 1,500 Methanol- 1, 500 Dicyclohexylamme caprylate. 200 N -hydroxyethyl oleamide 20 w 1,500
1,500 sampie Dicyclohexylamme eaprylate 11 Partly whlm spot rust Sodium bcnzoate Water 1,500 Methanol 1, 500 Dieyclohexylamlne caprylate 220 Water 1,500 Methanol 1, 500 N-hydroxyethyl oleamlde.-. 220 Sample Water 1, 500 Partly white spot rust.
Methanol 1,500 Sodium benzoate 220 We 1,500 M 1,500
Untreated aluminium White rust in total surface.
EXAMPLE 4 The various sample solutions listed in Table 4 below were prepared, 100 cc. of each of which were placed in a container measuring 9 cm. in inside diameter and cm. in height. A test piece of cold-roll steel measuring 6 cm. x 10 cm. x 0.2 cm. was introduced halfway into the container, and disposed thus for 30 consecutive days, with the upper half portions of the test piece exposed to the atmosphere. A blank test was also conducted with use of distilled water.
a fatty acid selected from the group consisting of the reaction products of amines having 6l2 carbon atoms and a saturated fatty acid having 618 carbon atoms, 20O parts by weight of an alkali metal benzoate, 1-50 parts by weight of an alkanolamide selected from the group consisting the reaction products of ethanolamines and a saturated fatty acid having 6-18 carbon atoms, and a mixture of alcohol and water in an amount to produce an 0.520% alcohol solution.
5. A rust-proofing composite solution as claimed in claim 4, wherein the alkali metal benzoate is selected Distilled water NOTE.-Corrosion-inhibitive factor is represented by rusttree surface area/test piece surface area X100.
What is claimed is:
1. A rust-proofing composite solution consisting essentially of 50-100 parts by weight of an amine salt of a fatty acid selected from the group consisting of the reaction products of amines having 6-12 carbon atoms and a saturated fatty acid having 6-18 carbon atoms, 20-200 parts by weight of an alkali metal benzoate, 1-50 parts by weight of an alkanolamide selected from the group consisting of the reaction products of ethanolamines and a saturated fatty acid having 6-18 carbon atoms, and water in an amount to produce an 05-20% aqueous solution.
2. A rust-proofing composite solution as claimed in claim 1, wherein the alkali metal benzoate is selected from the group consisting of sodium benzoate, potassium benzoate and lithium benzoate.
3. A rust-proofing composite solution as claimed in claim 2, wherein the amine salt of a fatty acid is selected from the group consisting of cyclohexylamine laurate, dicyclohexylamine caprylate, cyclohexylarnine myristate and octylamine stearate, and said alkanolamide is selected from the group consisting of N-hydroxyethyl olearnide, N,N-bis-hydroxyethyl capramide and N,N-bishydroxyethyl lauramide.
4. A rust-proofing composite solution consisting essentially of 50-100 parts by weight of an amine salt of References Cited UNITED STATES PATENTS 2,739,870 3/1956 Senkus 252392 2,782,164 2/1957 Fischer et al. 252-392 2,850,461 9/1958 Bloch et al. 252-394 RICHARD D. LOVERING, Primary Examiner I. GLUCK, Assistant Examiner U.S. Cl. X.R.