CA1292863C - Antifreeze concentrates and coolants containing heteropolymolybdatecompounds - Google Patents
Antifreeze concentrates and coolants containing heteropolymolybdatecompoundsInfo
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- CA1292863C CA1292863C CA000538160A CA538160A CA1292863C CA 1292863 C CA1292863 C CA 1292863C CA 000538160 A CA000538160 A CA 000538160A CA 538160 A CA538160 A CA 538160A CA 1292863 C CA1292863 C CA 1292863C
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Abstract
ANTIFREEZE CONCENTRATES AND COOLANTS
CONTAINING HETEROPOLYMOLYBDATE COMPOUNDS
Abstract of the Invention The subject invention relates to a polyhydroxy alcohol-based antifreeze concentrate for engines containing aluminum parts which utilizes certain heteropolymolybdate compounds as corrosion inhibitors for aluminum parts. In addition, the antifreeze contains conventional components such as a buffer, silicate, and nitrate.
CONTAINING HETEROPOLYMOLYBDATE COMPOUNDS
Abstract of the Invention The subject invention relates to a polyhydroxy alcohol-based antifreeze concentrate for engines containing aluminum parts which utilizes certain heteropolymolybdate compounds as corrosion inhibitors for aluminum parts. In addition, the antifreeze contains conventional components such as a buffer, silicate, and nitrate.
Description
~;~32863 -ANTIFREEZE CONCENTRATES AND COOLANTS
CONTAINING HETEROPOLYMOLYBDATE COMPOUNDS
Background of the Invention 1. Field of the Invention This invention relates to polyhydroxy alcohol-based antifreeze concentrates and coolants. Conventional components are used except for certain heteropolymolybdate compounds .
CONTAINING HETEROPOLYMOLYBDATE COMPOUNDS
Background of the Invention 1. Field of the Invention This invention relates to polyhydroxy alcohol-based antifreeze concentrates and coolants. Conventional components are used except for certain heteropolymolybdate compounds .
2. Description of the Prior Art Moly~dates, phosphates, and silicates are well known components of antifreeze to inhibit various types of corrosion. These inhibitors can be used individually or as mixtures, but thece is no apparent synergism which results from using mixtures.
Heteropolymolybdates are known compounds and have been used to lnhibit the corrosion of carbon steel in WatQr. See Xu et al, "Study of Heteropolymolybdates as Water Corrosion Inhibitors," Chemical A~stracts, Vol. 96, 129508h (1981).
Summary of the Invention The subject invention relates to polyhydroxy alcohol-based antifreeze concentrates for engines containing aluminum parts comprising:
(a) an effective corrosion inhibiting amount of a heteropolymolybdate compound having the following structural formula:
Heteropolymolybdates are known compounds and have been used to lnhibit the corrosion of carbon steel in WatQr. See Xu et al, "Study of Heteropolymolybdates as Water Corrosion Inhibitors," Chemical A~stracts, Vol. 96, 129508h (1981).
Summary of the Invention The subject invention relates to polyhydroxy alcohol-based antifreeze concentrates for engines containing aluminum parts comprising:
(a) an effective corrosion inhibiting amount of a heteropolymolybdate compound having the following structural formula:
3~
lZ9;2~63 [ X Mo 1240 ]
where xn+ = P+S or Si+4, tb) a buffer compound in an amount such that the RA of the antifreeze concentrate i~ at least 10, (c) from 0.1 to 1.0 weight percent of a nitrate, said weight percent based upon the total weight of the concentrate (d) water, and (e) one or more polyhydroxyl alcohols ~uch that the weight ratio o water to polyhydroxyl alcohol is from 0.1:100 to 10:100.
The heteropolymolybdates are effective inhibitors again~t solder corrosion and aluminum corrosion. Data sugge~ts they provide more effective corrosion protection than could have been predicted when considering the amount of active metal bonded in the heteropolymolybdate structure.
lZ9Z863 Descri tion of the Preferred Embodiments p The heteropolymolybdate compounds are known compound~' and are commercially available. Two of the best known, and, therefore, used on a preferred basis are 12-molybdophosphate and 12-molybdosilicate. Both of these compounds are available from AMAX Corporation. These compounds are used in an amount effective to inhibit the corrosion of aluminum metal parts. Generally, they are used in an amount of 0.1 weight percent to 1.0 weight percent, 1~ said weight percent based upon the total weight of the concentrate.
The buffer compound used may be a phosphate, borate, or carbonate in any o their avallable forms. The amount of buffer used ~s ~uch that the pH of the resulting coolant will havQ a reservQ alkalinity (RA) of at least 5 or a coolant and at lea~t 10 for a concentrate. RA i8 a measure of buffer capacity and 19 determined by titrating a 10 ml neat coolant sample (which is preferably diluted to 100 ml) with 0.1 N hydrochloric acid to a pH of 5.5. The milliliters of acid used is equal to the RA of the coolant.
A water-soluble nitrate, which i9 preferably used in a corrosion inhibiting amount to provide specific -'See Advanced Inorqanic Chemistr~, F.A. Cotton and G. Wilkinson, pp 949-957, Interscience Publishers, N.Y. (3rd edition, 1973).
12~2863 corrosion protection of aluminum, can be derived from any inorganic nitrate compound which i8 capable of ionization to provide nitrate ions in sufficient concentration to pass-ivate an aluminum or aluminum alloy surface. The water-soluble nitrate can be derived from nitric acid or an alkali metal or alkaline earth metal nitrate. Preferably, the water-soluble nitrate is an alkali metal nitrate. lt is possible to add nitric acid to the aqueous liquid and subsequently add an alkali or alkaline earth metal hydroxide to neutralize the nitric acid and obtain an aqueous solution having a pH in the desired pH range. Useful water-soluble nitrate salts are sodium nitrate, potassium nitrate, lithium nitrate, cesium nitrate, rubidium nitrate, calcium nitrate, strontium nitrate, and magnesium nltrate. Preferably sodium or potassium nitrate is utlllzed. q'he proportion of nitrate ion utillzed, calculated as sodium nitrate, is generally about 0.1 weight percent to about 1.0, preferably 0.1 weight percent to 0.5 weight percent based upon the weight of the antifreeze concentrate.
A water-soluble nitrite can be included optionally in the coolant compositions, antifreeze concentrates and metal corrosion inhibiting compositions of the invention as a specific corrosion inhibitor for cast iron and mild steel in contact with an aqueous liquid. Preferably, the water-soluble nitrites are alkali metal nitrites such as potassium and sodium nitrites. These corrosion inhibitors can be utilized generally in the antifreeze concentrates and coolant compositions of the invention in a proportion of about 0.05 weight percent to about 0.5 weight percent based upon the weight of the antifreeze concentrate.
The antifreeze concentrate preferably contains a water-soluble inorganic silicate represented by the average formula:
(M20) (SiO2)n wherein n has a value from 0.5 to 4, or preferably from 1.0 to 2.5 and wherein M is a cation that forms a water-soluble silicate and a is the valQnce of the catlon represented by M
and has a value of at least 1. Illustrative of these silicates are the alkali mQtal orthosllicates wherein M is an alkali metal and n is 1, the alkali metal metasilicates, the alkali metal tetrasilicates, the alkali metal disili-cates, and the tetra(organo) ammonium silicates. Specific examples of these silicates are potassium metasilicate, sodium orthosilicate, potassium disilicate, lithium ortho-silicate, lithium metasilicate, lithium disilicate, rubidium disilicate, rubidium tetrasilicate. tetra(methyl)ammonium silicate, tetra(ethyl)ammonium silicate, phenyltrimethyl ammonium silicate, benzyltrimethyl ammonium silicate, ~29Z~3~i3 guanidine silicate, and tetra(hydroxyethyl)ammonium silicate. The preferred silicates are sodium and potassium silicates, especially sodium metasilicate and pota~sium metasilicate. Particularly desirable are the commercially available sodium silicate aqueous solutions containing a weight ratio of ~ilicon dioxide to sodium oxide of 1.8:1, 2.5:1, and 3.22:1.
The amount of silicate used in the antifreeze composition is generally from 0.1 to 1.0 weight percent, said weight percent being based upon the total weight of the antifreeze concentrate.
In addition to the water-soluble silicate, the coolant preferably contains a siloxane which acts as a silicate stabilizer. Representative examples of siloxanes which can be used in conjunction with the silicate are found in U.S. Patents 4,362,644: 4,434,065: 2,968,643; 3,215,643:
3,341,469; 3,337,496: 3,312,622: 3,198,820: 3,203,969;
3,248,329: and 3,507,897. Ihe slLoxanes are used in amourlts such that the wei~llt ratio oE total silicate to siloxane in the antiFree~e conlpositlon i~ froln 2 to lO, preferably from 4 to 8.
Th~ antlfree~e concentrates utilize at least one water-soluble alcohol which i9 defined to include both monohydric alcohols (such as methanol, ethanol, and pro-~29ZE3~i3 panol) and polyhydric alcohol~ (such as ethylene glycol, dipropylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and glycerol). The alcohol can also include hydrocarbon alcohols and alcohols containing ether linkages. Mixtures of alcohols are also useful in the compo~itions of this invention. In view of it~ desirable physical properties such as its low molecular weight and its low volatility, ethylene glycol is an especially useful alcohol in these compositions and mixtures of ethylene lU glycol and diethylene glycol are preferred. Especially preferred are mixtures of about 80 percent to about 98 percent ethylene glycol and 2 percent to about 20 percent of diethylene glycol all by weight and based upon the total weight of the antifreeze concentrate.
The antifree2e concentrates are adapted or economical sh1pment and storagQ and can be diluted with watQr to orm coolants for use in the cooling systQms of water-cooled internal combustion engines. The antifree~e concentrate ha~ a weight ratio of water to polyhydroxy alcohol of 0.1:100 to 1:20, preferably from 1:50 to 1:20.
The antifree~e coolant has a weight ratio of water to polyhydroxy alcohol of from 1:2 to 4:1, preferably from 1:1 to 3:1.
To provide for the corrosion protection of copper, bra~s and solder, the coolants preferably contain in a 129Z8~3 corrosion inhibiting amount at least one water-soluble ~alt of a triazole or thiazole compound. Representative useful thiazoles include the alkali metal salts such as the sodium, potassium, lithium, rubidium, and cesium salts of thiazoles such as mercaptobenzothiazole, 4-phenyl-2-mercaptobenzothia-zole, 4-methyl-2-mercaptobenzothiazole, and 5-methyl-2-mercaptobenzothiazole. Representative useful triazoles include the alkali metal salt~ of benzotriazole, tolyl-triazole, benzotriazole carboxylic acid, alkyl esters of benzotriazole carboxylic acid having 1 to 8 carbon atoms in the alkyl group such as the methyl and butyl esters thereof, and ~enzotriazole derivatives having various substituents on the aromatic ring, i.e., N02, Cl, and NH2.
At least one thiazole or triazole compound can be lncorporated into the aqueou~ coolant or antlfreeze concen~
trate composition or into the corrosion inhiblting composi-tion intended or sub~equent addition to the cooling system of an internal combustion sy4tem in the acid form of the thiazole or triazole. In the resulting alkaline solution of the coolant or antifreeze concentrate or corrosion inhib-iting composition, the acid form is converted to the salt which is water soluble. The thiazole or triazole, calcu-lated as the sodium salt, i3 incorporated into the coolant solution and the antifreeze concentrate generally in the proportion of about 0.1 percent by weight to about 0.5 129Z~63 percent by weight based upon the weight of the concen-trate. Preferably, the proporation of thiazole or triazole is about 0.05 weight percent to about 0.5 weight percent and most preferably about 0.1 weight percent to about 0.25 weight percent, all based upon the weight of the antifreeze concentrate. The weight percent of the thiazole or triazole is calculated 90 as to provide an equivalent ion concentra-tion as would be provided by sodium mercaptobenzothiazole with respect to the thiazole compounds and sodium tolyltri-azole with respect to the triazole compounds.
Other conventional metal corrosion inhibitors, such as water-soluble molybdates and benzoates, particularly the alkali metal salts thereof can be used for thelr known metal corrosion inhibiting effects. Other special additives such as antifoam agents, identlying dyes, pH indicators, sealants which prevent leakage o the coolant from the coollng system, anticreep agents which prevent seepage of the coolant lnto the crankcase of the internal combustion engine, and the like, can be added to the heat-transfer compositions of the invention.
The corrosion inhibited heat transfer compositions of this invention can be prepared in any convenient manner by adding at ambient temperature and pressure the required metal corrosion inhibitors to water optionally containing a water-soluble alcohol and various conventional additives for ~Z9Z~63 imparting special properties to the heat-transfer medium.
The mixed liquid or solid metal corrosion inhibitor composi-tions can be prepared simply by combining dry or liquid forms of the components and mixing at ambient temperature and pressure until a uniform dry mixture or aqueou~ solution or di~persion of the components is obtained. Silicates in the absence of ~iloxanes, however, should not be exposed to a pH of <9.
Many metal corrosion-inhibiting compositions can be prepared in accordance with the teachings of the inven-tion. The following compo~itions are, therefore, merely representative. Where not otherwise specified throughout this specification and claims, temperatures are given in degreQs centigrade and parts, percentages, and proportions are by weight.
lZg2~3 Examples In the Examples which follow a base antifreeze was prepared having the following composition and an RA value of 7.7.
Amount Component (weight percent) Ethylene Glycol 93.5 Diethylene Glycol 5.0 NaN03 Borax 5 H2O l.O
Test antifreezes were prepared by adding various inhibitors to the ba~e antifreeze. These formulations are de~cribed ln Table I.
TABLE I
Amount of Inhibitor Example Inhibitor (weight percent) 1 12-molybdophosphatel.O
2 12-molybdosilicate 1.0 C-l 2 4 2 1.0 C-2 Na2HPO4 1.0 C-3 Na2SiO3 0 5 A screening te~t was then conducted on the foregoing antifreezes according to glavanostaircase polari-lZ~Z~363 zation method (GSCP) as described by S.T. Hirozawa in the article entitled "Galvano~taircase Polarization" in the Journal of the Electrochemical Society, Vol 130, No. 8, tAugust 1983), and in the paper delivered at the Corrosion 85 Symposium entitled "Corrosion Monitoring by Galvanostaircase Polarization" by S.T. Hirozawa, Paper No. 85.
Es3entially the test method lnvolves passing incrementally a current through a solder which is immersed in the test antifreeze to determine its breakdown poten-tial (~Eb) which is related to the general corrosion rate of the solder. The higher ~Eb, the greater the inhibition agalnst general corrosion. This test wa3 conducted with three different types of solder whose various concentratlons of metal~ is shown below:
Pb Sn Ag Solder A 96.5 3.0 0.5 Solder B 93.5 6.0 O.S
Solder C 70.0 30 0 ~EEb in ~able II which follows is expressed in millivolts.
The number in parenthese3 is the calculated ~Eb which would have been expected based upon the amount of molybdate, phosphate, and silicate in the heteropolymolybdate compound used and the ~Eb for an equivalent weight of these compounds ~ZS~2~f~i3 determined separately, i.e., as in Examples C-l, C-2, and C-3.
TABLE II
Solder A Solder B Solder C
Antifreeze (~Eb) (QEb) (~Eb) 1 710 tl40) 430 (71) 260 (98) 2 170 (136) 300 370 C-l 140 65 80 The test result~ show that in all cases the experimental value of ~Eb for the heteropolymolybdate was higher than the expected calculated value.
The test antireeze was then tested for sand abrasion as follows. Two preweighed 1" ~ections of aluminum radlator tube stock WerQ mounted on a specimen holder. They were vacuum-brazed by the usual heat cycle used in the fabrication of aluminum radiators. The specimen holders were then filled with about 900 milliliters of a solution made up from 1 part antifreeze in 5 parts 100-100-100 ASTM
corrosion test water and 5 grams of casting sand were added. Solutions were heated and maintained at 190F and pumped at a nozzle velocity of 443 centimeters/second for 24 lZ928~3 hours. The aluminum specimens were then removed from the holder and cleaned with chromic acid and reweighed. The weight loss is measured in milligrams. The numbers in parentheses are the calculated weight losses expected based upon the amounts of moly~date, phosphate, and silicate in the heteropolymolybdate and the weight 109s results from these compound~ when used separately. The test results are summarized in Ta~le III.
TABLE III
AntifreezeWeight Loss (mg) 1 20 (112) 2 38 (112) C-l 114 To test the stabillty o the heteropoly structure at a pH ~4.5, the following experiment was conducted. A
test solution was prepared having a pH of 8.5 containing 12-molydophosphate. The test solution was heat cycled four weeks (4 hours at 190F and 8 hours off). The sand abrasion test was then carried out at time 0, one week, two weeks, and four weeks on four different sample specimens. The results are given in Table IV.
~Z9Z863 TABLE IV
Period of Heat Cyclin~ Weight Loss, mq 1 week 36 2 weeks 28 4 weeks 28 The results indicate that the 12-molydophosphate i9 effec-tive at a high pH, and must, therefore, be ~table contrary to expert opinion.
lZ9;2~63 [ X Mo 1240 ]
where xn+ = P+S or Si+4, tb) a buffer compound in an amount such that the RA of the antifreeze concentrate i~ at least 10, (c) from 0.1 to 1.0 weight percent of a nitrate, said weight percent based upon the total weight of the concentrate (d) water, and (e) one or more polyhydroxyl alcohols ~uch that the weight ratio o water to polyhydroxyl alcohol is from 0.1:100 to 10:100.
The heteropolymolybdates are effective inhibitors again~t solder corrosion and aluminum corrosion. Data sugge~ts they provide more effective corrosion protection than could have been predicted when considering the amount of active metal bonded in the heteropolymolybdate structure.
lZ9Z863 Descri tion of the Preferred Embodiments p The heteropolymolybdate compounds are known compound~' and are commercially available. Two of the best known, and, therefore, used on a preferred basis are 12-molybdophosphate and 12-molybdosilicate. Both of these compounds are available from AMAX Corporation. These compounds are used in an amount effective to inhibit the corrosion of aluminum metal parts. Generally, they are used in an amount of 0.1 weight percent to 1.0 weight percent, 1~ said weight percent based upon the total weight of the concentrate.
The buffer compound used may be a phosphate, borate, or carbonate in any o their avallable forms. The amount of buffer used ~s ~uch that the pH of the resulting coolant will havQ a reservQ alkalinity (RA) of at least 5 or a coolant and at lea~t 10 for a concentrate. RA i8 a measure of buffer capacity and 19 determined by titrating a 10 ml neat coolant sample (which is preferably diluted to 100 ml) with 0.1 N hydrochloric acid to a pH of 5.5. The milliliters of acid used is equal to the RA of the coolant.
A water-soluble nitrate, which i9 preferably used in a corrosion inhibiting amount to provide specific -'See Advanced Inorqanic Chemistr~, F.A. Cotton and G. Wilkinson, pp 949-957, Interscience Publishers, N.Y. (3rd edition, 1973).
12~2863 corrosion protection of aluminum, can be derived from any inorganic nitrate compound which i8 capable of ionization to provide nitrate ions in sufficient concentration to pass-ivate an aluminum or aluminum alloy surface. The water-soluble nitrate can be derived from nitric acid or an alkali metal or alkaline earth metal nitrate. Preferably, the water-soluble nitrate is an alkali metal nitrate. lt is possible to add nitric acid to the aqueous liquid and subsequently add an alkali or alkaline earth metal hydroxide to neutralize the nitric acid and obtain an aqueous solution having a pH in the desired pH range. Useful water-soluble nitrate salts are sodium nitrate, potassium nitrate, lithium nitrate, cesium nitrate, rubidium nitrate, calcium nitrate, strontium nitrate, and magnesium nltrate. Preferably sodium or potassium nitrate is utlllzed. q'he proportion of nitrate ion utillzed, calculated as sodium nitrate, is generally about 0.1 weight percent to about 1.0, preferably 0.1 weight percent to 0.5 weight percent based upon the weight of the antifreeze concentrate.
A water-soluble nitrite can be included optionally in the coolant compositions, antifreeze concentrates and metal corrosion inhibiting compositions of the invention as a specific corrosion inhibitor for cast iron and mild steel in contact with an aqueous liquid. Preferably, the water-soluble nitrites are alkali metal nitrites such as potassium and sodium nitrites. These corrosion inhibitors can be utilized generally in the antifreeze concentrates and coolant compositions of the invention in a proportion of about 0.05 weight percent to about 0.5 weight percent based upon the weight of the antifreeze concentrate.
The antifreeze concentrate preferably contains a water-soluble inorganic silicate represented by the average formula:
(M20) (SiO2)n wherein n has a value from 0.5 to 4, or preferably from 1.0 to 2.5 and wherein M is a cation that forms a water-soluble silicate and a is the valQnce of the catlon represented by M
and has a value of at least 1. Illustrative of these silicates are the alkali mQtal orthosllicates wherein M is an alkali metal and n is 1, the alkali metal metasilicates, the alkali metal tetrasilicates, the alkali metal disili-cates, and the tetra(organo) ammonium silicates. Specific examples of these silicates are potassium metasilicate, sodium orthosilicate, potassium disilicate, lithium ortho-silicate, lithium metasilicate, lithium disilicate, rubidium disilicate, rubidium tetrasilicate. tetra(methyl)ammonium silicate, tetra(ethyl)ammonium silicate, phenyltrimethyl ammonium silicate, benzyltrimethyl ammonium silicate, ~29Z~3~i3 guanidine silicate, and tetra(hydroxyethyl)ammonium silicate. The preferred silicates are sodium and potassium silicates, especially sodium metasilicate and pota~sium metasilicate. Particularly desirable are the commercially available sodium silicate aqueous solutions containing a weight ratio of ~ilicon dioxide to sodium oxide of 1.8:1, 2.5:1, and 3.22:1.
The amount of silicate used in the antifreeze composition is generally from 0.1 to 1.0 weight percent, said weight percent being based upon the total weight of the antifreeze concentrate.
In addition to the water-soluble silicate, the coolant preferably contains a siloxane which acts as a silicate stabilizer. Representative examples of siloxanes which can be used in conjunction with the silicate are found in U.S. Patents 4,362,644: 4,434,065: 2,968,643; 3,215,643:
3,341,469; 3,337,496: 3,312,622: 3,198,820: 3,203,969;
3,248,329: and 3,507,897. Ihe slLoxanes are used in amourlts such that the wei~llt ratio oE total silicate to siloxane in the antiFree~e conlpositlon i~ froln 2 to lO, preferably from 4 to 8.
Th~ antlfree~e concentrates utilize at least one water-soluble alcohol which i9 defined to include both monohydric alcohols (such as methanol, ethanol, and pro-~29ZE3~i3 panol) and polyhydric alcohol~ (such as ethylene glycol, dipropylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and glycerol). The alcohol can also include hydrocarbon alcohols and alcohols containing ether linkages. Mixtures of alcohols are also useful in the compo~itions of this invention. In view of it~ desirable physical properties such as its low molecular weight and its low volatility, ethylene glycol is an especially useful alcohol in these compositions and mixtures of ethylene lU glycol and diethylene glycol are preferred. Especially preferred are mixtures of about 80 percent to about 98 percent ethylene glycol and 2 percent to about 20 percent of diethylene glycol all by weight and based upon the total weight of the antifreeze concentrate.
The antifree2e concentrates are adapted or economical sh1pment and storagQ and can be diluted with watQr to orm coolants for use in the cooling systQms of water-cooled internal combustion engines. The antifree~e concentrate ha~ a weight ratio of water to polyhydroxy alcohol of 0.1:100 to 1:20, preferably from 1:50 to 1:20.
The antifree~e coolant has a weight ratio of water to polyhydroxy alcohol of from 1:2 to 4:1, preferably from 1:1 to 3:1.
To provide for the corrosion protection of copper, bra~s and solder, the coolants preferably contain in a 129Z8~3 corrosion inhibiting amount at least one water-soluble ~alt of a triazole or thiazole compound. Representative useful thiazoles include the alkali metal salts such as the sodium, potassium, lithium, rubidium, and cesium salts of thiazoles such as mercaptobenzothiazole, 4-phenyl-2-mercaptobenzothia-zole, 4-methyl-2-mercaptobenzothiazole, and 5-methyl-2-mercaptobenzothiazole. Representative useful triazoles include the alkali metal salt~ of benzotriazole, tolyl-triazole, benzotriazole carboxylic acid, alkyl esters of benzotriazole carboxylic acid having 1 to 8 carbon atoms in the alkyl group such as the methyl and butyl esters thereof, and ~enzotriazole derivatives having various substituents on the aromatic ring, i.e., N02, Cl, and NH2.
At least one thiazole or triazole compound can be lncorporated into the aqueou~ coolant or antlfreeze concen~
trate composition or into the corrosion inhiblting composi-tion intended or sub~equent addition to the cooling system of an internal combustion sy4tem in the acid form of the thiazole or triazole. In the resulting alkaline solution of the coolant or antifreeze concentrate or corrosion inhib-iting composition, the acid form is converted to the salt which is water soluble. The thiazole or triazole, calcu-lated as the sodium salt, i3 incorporated into the coolant solution and the antifreeze concentrate generally in the proportion of about 0.1 percent by weight to about 0.5 129Z~63 percent by weight based upon the weight of the concen-trate. Preferably, the proporation of thiazole or triazole is about 0.05 weight percent to about 0.5 weight percent and most preferably about 0.1 weight percent to about 0.25 weight percent, all based upon the weight of the antifreeze concentrate. The weight percent of the thiazole or triazole is calculated 90 as to provide an equivalent ion concentra-tion as would be provided by sodium mercaptobenzothiazole with respect to the thiazole compounds and sodium tolyltri-azole with respect to the triazole compounds.
Other conventional metal corrosion inhibitors, such as water-soluble molybdates and benzoates, particularly the alkali metal salts thereof can be used for thelr known metal corrosion inhibiting effects. Other special additives such as antifoam agents, identlying dyes, pH indicators, sealants which prevent leakage o the coolant from the coollng system, anticreep agents which prevent seepage of the coolant lnto the crankcase of the internal combustion engine, and the like, can be added to the heat-transfer compositions of the invention.
The corrosion inhibited heat transfer compositions of this invention can be prepared in any convenient manner by adding at ambient temperature and pressure the required metal corrosion inhibitors to water optionally containing a water-soluble alcohol and various conventional additives for ~Z9Z~63 imparting special properties to the heat-transfer medium.
The mixed liquid or solid metal corrosion inhibitor composi-tions can be prepared simply by combining dry or liquid forms of the components and mixing at ambient temperature and pressure until a uniform dry mixture or aqueou~ solution or di~persion of the components is obtained. Silicates in the absence of ~iloxanes, however, should not be exposed to a pH of <9.
Many metal corrosion-inhibiting compositions can be prepared in accordance with the teachings of the inven-tion. The following compo~itions are, therefore, merely representative. Where not otherwise specified throughout this specification and claims, temperatures are given in degreQs centigrade and parts, percentages, and proportions are by weight.
lZg2~3 Examples In the Examples which follow a base antifreeze was prepared having the following composition and an RA value of 7.7.
Amount Component (weight percent) Ethylene Glycol 93.5 Diethylene Glycol 5.0 NaN03 Borax 5 H2O l.O
Test antifreezes were prepared by adding various inhibitors to the ba~e antifreeze. These formulations are de~cribed ln Table I.
TABLE I
Amount of Inhibitor Example Inhibitor (weight percent) 1 12-molybdophosphatel.O
2 12-molybdosilicate 1.0 C-l 2 4 2 1.0 C-2 Na2HPO4 1.0 C-3 Na2SiO3 0 5 A screening te~t was then conducted on the foregoing antifreezes according to glavanostaircase polari-lZ~Z~363 zation method (GSCP) as described by S.T. Hirozawa in the article entitled "Galvano~taircase Polarization" in the Journal of the Electrochemical Society, Vol 130, No. 8, tAugust 1983), and in the paper delivered at the Corrosion 85 Symposium entitled "Corrosion Monitoring by Galvanostaircase Polarization" by S.T. Hirozawa, Paper No. 85.
Es3entially the test method lnvolves passing incrementally a current through a solder which is immersed in the test antifreeze to determine its breakdown poten-tial (~Eb) which is related to the general corrosion rate of the solder. The higher ~Eb, the greater the inhibition agalnst general corrosion. This test wa3 conducted with three different types of solder whose various concentratlons of metal~ is shown below:
Pb Sn Ag Solder A 96.5 3.0 0.5 Solder B 93.5 6.0 O.S
Solder C 70.0 30 0 ~EEb in ~able II which follows is expressed in millivolts.
The number in parenthese3 is the calculated ~Eb which would have been expected based upon the amount of molybdate, phosphate, and silicate in the heteropolymolybdate compound used and the ~Eb for an equivalent weight of these compounds ~ZS~2~f~i3 determined separately, i.e., as in Examples C-l, C-2, and C-3.
TABLE II
Solder A Solder B Solder C
Antifreeze (~Eb) (QEb) (~Eb) 1 710 tl40) 430 (71) 260 (98) 2 170 (136) 300 370 C-l 140 65 80 The test result~ show that in all cases the experimental value of ~Eb for the heteropolymolybdate was higher than the expected calculated value.
The test antireeze was then tested for sand abrasion as follows. Two preweighed 1" ~ections of aluminum radlator tube stock WerQ mounted on a specimen holder. They were vacuum-brazed by the usual heat cycle used in the fabrication of aluminum radiators. The specimen holders were then filled with about 900 milliliters of a solution made up from 1 part antifreeze in 5 parts 100-100-100 ASTM
corrosion test water and 5 grams of casting sand were added. Solutions were heated and maintained at 190F and pumped at a nozzle velocity of 443 centimeters/second for 24 lZ928~3 hours. The aluminum specimens were then removed from the holder and cleaned with chromic acid and reweighed. The weight loss is measured in milligrams. The numbers in parentheses are the calculated weight losses expected based upon the amounts of moly~date, phosphate, and silicate in the heteropolymolybdate and the weight 109s results from these compound~ when used separately. The test results are summarized in Ta~le III.
TABLE III
AntifreezeWeight Loss (mg) 1 20 (112) 2 38 (112) C-l 114 To test the stabillty o the heteropoly structure at a pH ~4.5, the following experiment was conducted. A
test solution was prepared having a pH of 8.5 containing 12-molydophosphate. The test solution was heat cycled four weeks (4 hours at 190F and 8 hours off). The sand abrasion test was then carried out at time 0, one week, two weeks, and four weeks on four different sample specimens. The results are given in Table IV.
~Z9Z863 TABLE IV
Period of Heat Cyclin~ Weight Loss, mq 1 week 36 2 weeks 28 4 weeks 28 The results indicate that the 12-molydophosphate i9 effec-tive at a high pH, and must, therefore, be ~table contrary to expert opinion.
Claims (12)
1. A polyhydroxy alcohol-based antifreeze concentrate for engines containing aluminum parts com-prising:
(a) an effective corrosion inhibiting amount of a heteropolymolybdate compound having the following structural formula:
[Xn+Mo12O40](8-n-1 where Xn+ - P+5 or Si+4;
(b) a buffer compound in an amount such that the RA of the antifreeze concentrate is at least 10;
(c) from 0.1 to 1.0 weight percent of a nitrate, said weight percent based upon the total weight of the concentrate;
(d) water; and (e) one or more polyhydroxyl alcohols such that the weight ratio of water to polyhydroxyl alcohol is from 0.1:100 to 10:100.
(a) an effective corrosion inhibiting amount of a heteropolymolybdate compound having the following structural formula:
[Xn+Mo12O40](8-n-1 where Xn+ - P+5 or Si+4;
(b) a buffer compound in an amount such that the RA of the antifreeze concentrate is at least 10;
(c) from 0.1 to 1.0 weight percent of a nitrate, said weight percent based upon the total weight of the concentrate;
(d) water; and (e) one or more polyhydroxyl alcohols such that the weight ratio of water to polyhydroxyl alcohol is from 0.1:100 to 10:100.
2. The antifreeze concentrate of claim 1 wherein the heteropolymolybdate compound is selected from the group consisting of 12- molybdosilicate, 12- molybdophosphate, and mixtures thereof.
3. The antifreeze concentrate of claim 2 wherein from 0.1 weight percent to 1.0 weight percent of a water-soluble inorganic silicate is used as an additional compo-nent.
4. The antifreeze concentrate of claim 3 wherein a siloxane is also used in the formulation and 19 present in an amount such that the weight ratio of total silicate to siloxane in the coolant is from 2 to 10.
5. The antifreeze concentrate of claim 4 wherein the heteropolymolybdate is used in amount of 0.1 percent by weight to 1.0 percent by weight, said percent by weight being based upon the total weight of the concentrate.
6. The antifreeze concentrate of claim 5 wherein additional corrosion inhibitors selected from the group consisting of nitrites, triazoles, and mixtures thereof are used in effective amounts.
7. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 1 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
8. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 2 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
9. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 3 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
10. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 4 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
11. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 5 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
12. An antifreeze coolant prepared by diluting the antifreeze concentrate of claim 6 with water such that the ratio of water to polyhydroxy alcohol is from 0.5:1 to 8:1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000538160A CA1292863C (en) | 1987-05-27 | 1987-05-27 | Antifreeze concentrates and coolants containing heteropolymolybdatecompounds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000538160A CA1292863C (en) | 1987-05-27 | 1987-05-27 | Antifreeze concentrates and coolants containing heteropolymolybdatecompounds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292863C true CA1292863C (en) | 1991-12-10 |
Family
ID=4135761
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000538160A Expired - Lifetime CA1292863C (en) | 1987-05-27 | 1987-05-27 | Antifreeze concentrates and coolants containing heteropolymolybdatecompounds |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1292863C (en) |
-
1987
- 1987-05-27 CA CA000538160A patent/CA1292863C/en not_active Expired - Lifetime
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