CA1057943A

CA1057943A - Multipurpose additive for automotive cooling systems

Info

Publication number: CA1057943A
Application number: CA234,573A
Authority: CA
Inventors: Alfred W. Oberhofer; Steven L. Stone
Original assignee: Nalco Chemical Co
Current assignee: ChampionX LLC
Priority date: 1974-09-18
Filing date: 1975-09-02
Publication date: 1979-07-10

Abstract

ABSTRACT OF THE DISCLOSURE

Corrosion inhibiting compositions and methods of using same in automobile coolant systems of the following composition:

Description

)5'7~43 . .

The present invention lies in improved corrosion inhibitor compositions for internal combustion engines for auto-mobiles. The pH is specially selected and adjusted (by alkaline carbonates and hyd~oxides) for an alkaline in-use range of between 10-12, preferably between 10-11, with the specific pre-ferred range of 10.4-10.8.
The supplemental alkalinity in the present composition serves to combat the thermal and chemical decomposition engendered by the higher skin temperatures of heat transfer surfaces in the passenger car engine and the normally higher temperatures encountered in trucks. It is noted that J. I. Bregman in Corrosion Inhibitors, MacMillan, 1963, states at pages 144-145 that conventionally the boron-nitrite inhibitors are used at a pH range of 8.5-9.5 usually by a buffer combination of borax and sodium nitrite. The supplemental alkalinity of these compo-sitions also works to lncrease the time in use, making changes of coolant fluid more infrequent despite the higher temperature ?
operating conditions.
The subject of satisfactory prevention of corrosion in coolant systems of modern automobiles has been noted in recent technic,al discussion. For example, in Chemical Week of ~uly 17, 1974, ~n an article entitled, "Auto Coolant Controversy Boils Over," the need for more effective coolants has been highlighted by the fact that today 72 percent of all U.S. built cars are equipped with air conditioners and the operating temperatures of the 1975 models are expected to be as high as 225F. The hotter engines of the new cars require greater protection for the coolant. This article further notes that in a current 1974 survey, a greater loss of reserve alk~linity (inhibitor capa-30 ¦ ¦bil y) a= well as greater quantitiqs ~f rust and sed ment in , , , 7~
the cooling system had occurred than in the same survey taken ten years ago. The present invention contemplates a multicomponent corrosion inhibitor of the following formulation, the liquid version of which is:

FO~ULATION I
Necessary Percent Soft Water 75-85 Alkali Metal Nitrite 1-3 Alkali Metal Silicate 1-5 ~lkaliJ Metal Hydroxide (50% by wt. caustic) .25-3.5~.
Sulfur Containing Copper Inhibitor .5-1.5 Borax 1-10 Polymeric Suppressant .1-1.0 Polymeric Dispersant .1-.5 Optional Sodium Oleate 1-3 Sodium Carbonate 1-3 Antifoam .05-.1 Dialkylaminoethanol .5-1 Dye . .05-.1 .. , . . _ . , .
'~ .

and the solid version of which is:
FORMULATION II
Necessary Percent Alkali Metal Nitrite 10-20 Alkali Metal Sllicate 5-25 Alkali Metal Hydroxide (50% by wt. caustic) 7.5-17.5 Sulfur Containing Copper Inhibitor 2.5-7.5 Borax 5~50 Polymeric Suppressant .5~5.0 Polymeric Dispersant .5-2.5 Optional Sodium Oleate 5-15 Sodium Carbonate 5-15 Antifoam .25-.5 Dialkylaminoethanol 2.5-5 Dye .25-.5 wherein the polymeric suppressant comprises a homopolymer of maleic anhydride, or a copolymer of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene or a vinyl ether, and the polymRric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxy-methyll cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.
In the above Formulations I and II, the alkalinity in use in the coolant is of prime importance and the composition of the premix ingredients are adjusted chiefly by the alkali metal hydroxide and carbonate content so that the pH in use is targeted for a pH of 10-12 or preferably 10-11. The solid composition (II above) may be incorporated into a pellet and placed in a spin-on or cartridge-type filter which serves for unitary replacemRnt in an engine cooling system.

, :

)5~ 3 PRIOR ART

The prior patented art believed pertinent to this application is as follows:
~ 2,723,956 ~ohnson (National Aluminate) Styrene maleic anhydride (SMA) for reducing scale in steam boilers.

2,815,328 Green et al (Nalco) A basic corrosion inhibitor for diesel engine cooling systems.
/ ~,877,188 Liddell (Hagan Chemicals) _~
Mercaptobenzothiazole as a copper inhibitor.
; 2,972,581 Johnson et al (Nalco) A multicomponent corrosion inhibiting com-position for diesel and auto cooling systems.

3,645,402 Alexander et al (Mack Trucks) Disposable-type filter for an internal combustion engine having a canister contain-ing a chemical corrosion inhibitor in a pallet preferably spun on to an adapter.

In contrast to the prior art noted above, the present formulations are constituted or made up so that a high pH is obtained of from about 12-12.5 and a use level pH (in deionized water) is obtained in the range 10-llj or more preferably 10.4-10.8. What is meant by a use level pH is that pH obtained by adding the equivalént of 4 fluid ounces of inhibitor composition per gallon of coolant and measuring the resulting pH.
In a most preferred formulation, in order to better protect copper, the present formulations substitute a L'i ~
monoaryltria~ole such as benzotriazole and tolyl triazole for a portion of the mercaptobenzothiazole formerly generally utilized.
Also, as an added facet there is added a polymeric dispersant to assist in the dispersing of solid particles in the coolant and such dispersant is selected from the group consisting of polyacrylates, a methacrylate-acrylate copolymer, and carboxymethyl cellulose, which are water soluble and have a preferred molecular weight of between 2,000 and 50,000.
In providing corrosion protection designed specially for automoti,ve engine systems, a composition must provide pro-tection for multiple surfaces. For example, the following metals are typical of those found in automotive systems:
aluminum, steel, copper, brass, cast iron, solder, and magnesium.
Additionally, in auto systems, the conventional use of so-called "permanent" ethylene glycol antifreeze in the systems produces by oxidation of the glycol a mixture of corrosive acids, including formic, which, if-uninhibited~ will be more corrosive than tap water to which no antifreeze had been added.

NECESSARY INGREDIENTS

2~ Alkali metal nitrite. Sodium nitrite and potassium nitrite are utilized to inhibit corrosion of iron and other metals.l These components are most efficient in the alkaline range.
Alkali metal silicate. Potassium and sodium silicates . .. ... . .
are preferred. The alkali silicates, such as sodium metasilicate, also provide one source of buffering for the acids produced from the glycol antifreeze in the system. Prime anti-corrosion targets for the silicates utilized in the present compositions are aluminum, iron, and solder, and here the silicate is believed 5'^~

~o operate by thin film protection best at the alkaline pH
targeted for the compositions of the present in~ention.
Alkali metal hydroxides and carbonates. These alkaline components are used as pH regulators to produce the desired working alkaline pH which is preferably about 10.4 to 10.8. The carbonate is utilized optionally in these formulations to pro-vide additional buffering action, together with borax, metaborate, or tetraborate.
In this specification the term "alkali metal" is limited to~the commercially feasible members comprising sodium and potassium, and MeOH designates alkali metal hydroxide.
Borax. The use of borax and similar boron compounds of l .
.j metaborate and tetraborate is helpful in a recirculating water , system by inhibiting steel and zinc and additionally supplying buffering capacity in alkaline pH's.
Sulfur containing copper inhibitor. The utilization of compounds containing sulfur as an inhibitor for corrosion of ;
copper materials in automobile engines has been well described.
For example, -2,198,151 Beekhuis et al describes potassium xanthate, thio acetic acid, thiourea, and thio acetamide.
2,963,432 and 2,963,433 Little et al teach ~lkyldithio) benzimidazole specifically as corrosion inhibitors for copper.
Both are nitrogen heterocycles which also contain divalent sulfur.
3,408,307 Troscinski et al describes tetrazoles.
3,598,756 Heit describes mixutres of mercaptobenzo-thiazole and dibutylthiourea.
3,755,176 Kinney et al describes thiohydrocarbyl acid or amine salts.
3,809,655 Williams describes dialkyl sulfides and di- -alkyl sulfoxides.
11 ' I

l~S'~

Additionally, Bregman, ante, at pages 115-116, recognizes that commercially the best corrosion inhibitor for copper today is 2-mercaptobenzothiazole, which is not only anodic inhibitor for copper but acts as a glycol oxidant inhibitor to prevent or inhibit the oxidation of any glycol anti-freeze normally present in auto systems. It has been theorized that the presence of a ring sulfur and nitrogen and with an ionizable sulfur in the formula ~ N ~

~,~ \ S

makes possible multiple sites for formation of coordinate bonds with copper.
In the present invention a preferred substitution for mercaptobenzothiazole is made by using a monoaryltriazole such as benzotriazole or tolyltriazole. Due to the increased heat in the automotive cooling system, it has been found that greater stability is achieved by utilizing these more heat stable com-pound,s in lieu of the more heat fragile mercaptobenzothiaæole. A
porti~n of the MBT is retained by a split dosage with one of the monoaryltriazoles due to more rapid action of MBT in an optimum formulation. A formulation of equiparts by weight of MBT and a monoaryltriazole has been found especially useful. This group of sulfur containing compounds are designated "sulfur containing copper corrosion inhibitors" and in one preferred sense are N-heterocycles containing sulfur.
Suppressant. Preferred suppressants are maleic anhydride polymers. Especially useful maleic anhydride polymers are selected from the group consisting of homopolymers of maleic ~7S 7~

anhydride, and copolymers of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene, and vinyl ethers. These polymers can be easily pre-pared according to standard methods of polymerization. In addition to synthetic polymers, natural polymers could also be useful, such as tannins and modified tannins, lignins and lignosulfonates, and water-soluble gums and starches.
Dispersant. The dispersant can be selected from the group consisting of polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose which are water-soluble and have an average molecular weight in the range of about 2,000 to 50,000.
OPTIONAL INGREDIENTS
The optional ingredients of the present formulations include an antifoam agent, dialkylaminoethanol, sodium oleate, alkali metal carbonates such as discussed above under "Hydroxides" as well as a small amount of an identifying dye.
The antifoam utilized is preferably a polyoxyalkylene glycol or diether thereof or a polypropylene glycol-ethyleneoxide condensate or other conventional commercial antifoams. Such a suitable antifoam is Ucon 50 B 5100*, a polyalkylene glycol (Union Carbide).
As a specific inhibitor targeted to protect solder, a minor perce~tage of a dialkylaminoethanol is optionally utilized. In this case ~he alkyl group is lower alkyl (Cl - C6) and specific examples of the solder protector are diethylaminoethanol, dipropylaminoethanol, dibutylaminoethanol, dimethylaminoethanol, etc.
The function of sodium oleate as an optional ingredient is also to protect solder.

*Trade r~ark -- ~
1I~5~3 FO~ AND DOSAGE

The format for including the corrosion inhibitor in the automobile coolant system is either liquid or solid and the composition is utilized in a dosage of 2-4 fluid ounces per gallon of coolant with a preferred dosage of about 4 fluid ounces per gallon. For shipping and installation, a compact unit together with a solids filter is preferred and an example where the chemical container is spun on to a ratchet in the filter is noted in 3,645,402 Alexander, noted ante. Such a compact unit solves many o~ the~problems arising in current cooling systems by ~
raising the pH to at least 10.4-10.8, supplying more inhibitor and re~oving suspended precipitates from antifreeze by means of a filter.

. . .
.

7~'~3 ..

A liquid corrosion inhibitor which exhibited a broad pH of 12-12.5 and a use pH of about 10.6 was prepared by utilizing the components below in the order o addition noted to produce a liquid product:
Water (preferably soft or deionized water~ 81.2~-%

Antifoam (Ucon 50 HB 5100--polyalkylene glycol) 0.1 %
Alkali~metal hydroxide (50% by wt. caustic) 2.7 %
Benzotriazole as copper inhibitor0.5 %
Mercaptobenzothiazole as copper inhibitor 0.5 %
Borax 6.0 %
Sodium metasilicate 3~5 %
Sodium nitrite 3.0 %
Styrene maleic anhydride 0.5 %
Dye .08%
Sodium polyacrylate 0.3 %
An additional experiment utilized tolyltriazole for benzo-triazole in the above formulation and further experiments added 2 percent of sodium oleate as a solder protector and 1 percent of dia1kylaminoethanol also as a solder protector. The necessary ingred~ents were varied within the limits set out in Formulation I
ante.-~ 2-' ¦ A solid corrosion inhibitor formulation was prepared utilizing the same ~rder of addition of ingredients as Exam~le 1 but deleting water as follows:
Antifoam (Ucon 50 ~B 5100--polyalkylene 0 5 glycol~
Alkali metal hydroxide (50% by wt, caustic) 13.5 %
~enzo~iazale as copper inhibitor 2.5 %
Nercapt~be~zothiazole as copper inhibitor 2.5 Borax ~ 30.0 %
lU Sodium metasilicate 17.5 %
Sod,ium nitrite 15.0 ~ , Styrene maleic anhydride ' ' 2.5 %
Dye '4 %
Sodium polyacrylate 1.5 % ' In this case the final product had a pH of about 12.3.
This formulation was varied within the limits of Formulation II.
. .
EXAMoeLE 3 Twelve ounces of the preparation of Example 2 were made up into a chemical package or pallet and placed into a disposable' type filter particularly adapted for use in the cooling systems of automlobile engines. The filter was inserted into the cooling system of a 1968 standard Thunderbird (Ford Motor Company) and the filter was changed every six months to observe'preci~itate and general condition of the coolant which proved satisfactory.
The filter is available commercial,ly from Mack Trucks, Inc., and is further described in 3,645,402 Alexander.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A corrosion inhibiting composition useful in automobile coolant systems characterized by a high use level pH of from 10-12 and consisting essentially of:

wherein the polymeric suppressant comprises a homopolymer of maleic anhydride, or a copolymer of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene or a vinyl ether, and the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

2. The corrosion inhibiting composition according to claim 1 con-sisting essentially of:

wherein the polymeric suppressant comprises a homopolymer of maleic anhydride, or a copolymer of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene or a vinyl ether, and the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

3. The corrosion inhibiting composition according to claim 1 con-sisting essentially of:
(Table continued) wherein the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

4. The corrosion inhibiting composition according to claim 1 wherein the sulfur containing copper inhibitor is a mixture of a mono-aryltriazole and mercaptobenzothiazole.

5. The corrosion inhibiting composition according to claim 4 wherein the sulfur containing copper inhibitor consists of about equal weight percents of a mercaptobenzothiazole and a monoaryltriazole selected from at least one member of a group consisting of benzotriazole and tolyltriazole.

6. A solid corrosion inhibiting composition useful in automotive cooling systems at a high use pH of 10-12 and consisting essentially of the following ingredients:
(Table continued) wherein the polymeric suppressant comprises a homopolymer of maleic anhydride, or a copolymer of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene or a vinyl ether, and the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

7. The solid corrosion inhibiting composition according to claim 6 wherein the sulfur containing copper inhibitor consists of a monoaryltria-zole and mercaptobenzothiazole.

8. The solid corrosion inhibiting composition according to claim 6 wherein the sulfur containing copper inhibitor consists of about equal weight percents of a mercaptobenzothiazole and a monoaryltriazole selected from at least one member of a group consisting of benzotriazole and tolyltriazole.

9. The solid corrosion inhibiting composition according to claim 6 consisting essentially of:
(Table continued) wherein the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

10. The composition of claim 6 which is incorporated into a unitary cartridge filter.

11. The composition of claim 9 which is incorporated into a unitary cartridge filter.

12. A method of inhibiting corrosion in automotive cooling systems containing cooling fluid which comprises adding thereto from 2-4 fluid ounces per gallon of a composition consisting essentially of the following ingredients:
(Table continued) wherein the polymeric suppressant comprises a homopolymer of maleic anhydride, or a copolymer of maleic anhydride with vinyl acetate, styrene, ethylene, isobutylene or a vinyl ether, and the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.

13. The method according to claim 12 wherein the composition consists essentially of:
wherein the polymeric dispersant is chosen from the group comprising polyacrylates, methacrylate-acrylate copolymers, and carboxymethyl cellulose; is water soluble; and has an average molecular weight in the range of from about 2,000 to about 50,000.