1、Designation: D 1121 07Standard Test Method forReserve Alkalinity of Engine Coolants and Antirusts1This standard is issued under the fixed designation D 1121; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers the determination of the
3、reservealkalinity of new, unused engine coolants, and liquid antirustsas received, of used or unused aqueous dilutions of theconcentrated materials, and of aqueous dilutions of solidantirusts.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to ad
4、dress all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1123 Test
5、Methods for Water in Engine Coolant Concen-trate by the Karl Fischer Reagent MethodD 1176 Practice for Sampling and Preparing Aqueous So-lutions of Engine Coolants or Antirusts for Testing Pur-posesD 1287 Test Method for pH of Engine Coolants and Anti-rusts3. Terminology3.1 Definition:3.1.1 reserve
6、alkalinity, na term applied to engine coolantconcentrates and antirusts to indicate the amount of alkalineinhibitors present in the product.4. Summary of Test Method4.1 A 10-mL sample of concentrated coolant, antirust,coolant additive, or an aqueous engine coolant containing theseproducts, is dilute
7、d to about 100 mL with water and titratedpotentiometrically with 0.100 N hydrochloric acid to a pH of5.5. The volume of acid used is reported to the nearest 0.1 mL.The concentration of coolant or additive in the coolant solutionshall be recorded if required, for calculation of depletion of thereserv
8、e alkalinity during performance tests.5. Significance and Use5.1 Reserve alkalinity is the number of millilitres, to thenearest 0.1 mL of 0.100 N hydrochloric acid (HCl) required forthe titration to a pH of 5.5 of a 10-mL sample of an undiluted,unused coolant, antirust, or coolant additive, and unus
9、ed orused solutions thereof.5.2 Reserve alkalinity is a term applied to engine coolantsand antirusts to indicate the amount of alkaline componentspresent in the product. It is frequently used for quality controlduring production, and values are often listed in specifications.When applied to used sol
10、utions, reserve alkalinity gives anapproximate indication of the amount of remaining alkalinecomponents. Unfortunately, the term is sometimes misused inthat its numerical value is said to be directly related to coolantquality, the higher the number, the better the coolant. ASTMCommittee D-15 on Engi
11、ne Coolants believes there is a need tocorrect some misconceptions and place the term in its properperspective.5.3 Reserve alkalinity (R.A.) as defined in Section 3 of thismethod is the number of millilitres of 0.1-N hydrochloric acidrequired to titrate 10 mL of concentrated coolant to a pH of 5.5.T
12、he term is not a completely accurate description of theproperty being measured because “alkalinity” usually refers tothe pH range above 7.0.5.4 A review of the origin of the term may be helpful inattempting to understand its proper use. When ethylene glycolwas first used as an engine coolant, it was
13、 uninhibited. Theneed for inhibition soon became apparent and triethanolaminewas incorporated. When solutions of this inhibited glycol weretitrated with dilute hydrochloric acid, it was found that thesteepest part of the neutralization curve occurred at a pH ofabout 5.0. Following the introduction o
14、f triethanolamine, otherbuffers, such as borates and phosphates, have been used.Titration to 5.5 was employed with these buffers which have anend point close to 5.5.1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and is the direct responsibility of Subcommittee D1
15、5.04 on ChemicalProperties.Current edition approved April 1, 2007. Published April 2007. Originallyapproved in 1950. Last previous edition approved in 2003 as D 1121 98(2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
16、 Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5 Generally, most metals in an automotive cooling systemcorrode less
17、in solutions which are mildly alkaline. Thecommonly used alkaline buffers, borates and phosphates, helpto maintain this desirable alkalinity and a stable pH forsubstantial additions of acid. A well inhibited coolant containssmaller amounts of other inhibitors (in addition to the buffers),to give bro
18、ad range corrosion protection for all of the metalsfound in the cooling system. These additional inhibitors maycontribute very little to the titration, but they can provideexcellent corrosion protection.5.6 The alkaline inhibitors provide buffering action andneutralize acids introduced into the cool
19、ant by exhaust gasleakage, by residual acid cleaner, or by the oxidation ofethylene glycol and propylene glycol. Some inhibitors whichcontribute little or no reserve alkalinity may give excellentcorrosion protection to certain metals but have little capacity tocombat acid contamination. In view of t
20、his, the magnitude ofthe R. A. in a coolant is not always a good criterion indetermining its potential protective properties.5.7 In summary, the precaution against the misuse of reservealkalinity is that the reserve alkalinity of an engine coolantsolution is not a dependable measure of its ability t
21、o preventcorrosion, nor can it satisfactorily indicate the additional life ofthe solution.6. Apparatus6.1 The pH meter, glass electrode, and calomel electrode,shall be as specified in the section on Apparatus (Section 5) ofTest Method D 1287.6.2 It is recognized that many laboratories use a combina-
22、tion electrode system for measuring the reserve alkalinity ofengine coolants. It should be noted that results obtained fromusing a combination electrode system have been found to bestatistically different from results obtained when using thecalomel and reference electrode system.37. Reagents7.1 Puri
23、ty of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused,
24、 provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterReferences to water shall be under-stood to mean distilled water or water of equal purity. Distilledwater shall be boiled thoroughl
25、y, or purged with carbondioxide-free air, to remove carbon dioxide, and shall beprotected with a soda-lime tube or the equivalent while coolingand in storage. The pH of the water shall be between 6.2 and7.2 at 25C. Take precautions to prevent contamination of thedistilled water with traces of the ma
26、terial used for protectionagainst carbon dioxide.7.3 Standard Buffer Solution5The buffer solutions forchecking pH assemblies and glass electrodes shall be stored inbottles of chemically resistant glass or polyethylene and shallbe prepared from salts sold specifically for use, either singly orin comb
27、ination, as pH standards. The salts shall be dried for 1h at 110C before use.7.4 Hydrochloric Acid (0.100 N)Prepare and standardize0.100 N hydrochloric acid (HCl).7.5 Phthalate Buffer Solution (0.05 M, pH = 4.01 at25C)Dissolve 10.21 g of potassium hydrogen phthalate indistilled water and dilute to 1
28、 L.7.6 Phosphate Buffer Solution (0.025 M with respect toeach phosphate salt, pH = 6.86 at 25C)Dissolve 3.40 g ofpotassium dihydrogen phosphate (KH2PO4) and 3.55 g ofanhydrous disodium hydrogen phosphate (Na2HPO4) in dis-tilled water and dilute to 1 L.7.7 Potassium Chloride ElectrolytePrepare a satu
29、ratedsolution of potassium chloride (KCl) in water.8. Sampling8.1 Sample the material in accordance with Standard Prac-tice D 1176.9. Preparation of Electrode System9.1 Maintenance of ElectrodesClean the glass electrodesat frequent intervals (not less than once every week duringcontinual use) in acc
30、ordance with the manufacturers instruc-tions. Drain the calomel electrodes at least once each week andfill with KCl electrolyte. Keep the electrolyte level in thecalomel electrode above that of the liquid in the titration beakerat all times. When not in use, immerse the lower half of theelectrodes i
31、n water and do not allow them to be immersed inthe titrated solution for any appreciable period of time betweentitrations. Although the electrodes are not extremely fragile,they should be handled carefully at all times.9.2 Preparation of ElectrodesBefore and after using, blotthe glass electrode thor
32、oughly with a clean cloth, or a soft,absorbent tissue, and rinse with water. Blot the calomelreference electrode with a cloth or tissue; carefully remove theground-glass sleeve and thoroughly blot both ground-glasssurfaces. Replace the sleeve loosely and allow a few drops ofelectrolyte to drain thro
33、ugh to flush the ground-glass joint. Wetthe ground surfaces thoroughly with electrolyte, set the sleevefirmly in place, and rinse the electrode with water. Prior to eachtitration, soak the prepared electrode in water for at least 2 min.Immediately before use, touch the tips of the electrodes with ad
34、ry cloth or tissue to remove excess water.10. Electrode System in pH Units10.1 Turn on the instrument, allow to warm up, and adjustin accordance with the manufacturers instructions. Allowsufficient time for the temperature of the buffer solution andimmersed electrodes to equalize and set the tempera
35、ture knob3Refer to ASTM Report RR:D15-1004.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Do
36、rset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Commercially available buffer tablets or prepared buffer solutions may be used.D1121072at the temperature of the buffer solution. Calibrate the assem-bly with a minimum of
37、two buffer solutions to check thelinearity of the response of the electrode or incorrect tempera-ture compensation. The presence of a faulty electrode isindicated by a failure to obtain a reasonably correct value forpH of the second standard solution when the meter has beenstandardized with the firs
38、t. A cracked electrode will often yieldpH values that are essentially the same for both standards.Adjust the standardization or asymmetry potential control untilthe reading of the dial corresponds to the known pH of thestandardizing buffer solution.11. Procedure11.1 Pipet 10 mL of a thoroughly mixed
39、 sample into a 250mL tall-form spout-less beaker. Allow 1 minute drain time.Add about 90 mL of distilled water (Note 2).NOTE 1The amount of water added is not critical; however, it must besufficient to cover the electrode tips. If the reserve alkalinity is less than2, the sample size may be increase
40、d to 50 mL diluted to 100 mL withwater, and the total titration divided by 5 to give the reserve alkalinity asdefined.11.2 Prepare the calomel and glass electrode as described inSection 9. Place the beaker containing the test solution on thetitration stand, adjust so that the lower half of each elec
41、trode isimmersed, start the stirrer, and adjust the rate of the stirring sothat there is vigorous stirring without spattering. Fill the 50-mLburet with standardized 0.100 N HCl. The normality of the acidused may be in the range from 0.095 to 0.105, but the actualtitration will require correction to
42、give the equivalent titrationwith 0.100 N acid. Position the buret tip inside the beaker.Adjust the pH meter temperature compensator to agree with thesolution temperature. Record the initial pH and proceed withthe titration to a pH of about 7. Use a slow, drop wise titrationrate from pH 7 to approac
43、h the end point of pH 5.5. Record thevolume of acid used, acid normality, and sample size. Switchthe pH meter to standby and rinse the electrodes with water anddry with clean absorbent material before the next determina-tion. When the pH meter is not in use, immerse the electrodesin distilled water.
44、 When a large number of reserve alkalinitydeterminations are made during a period of several hours, it isrecommended that the meter be recalibrated at various intervalsas described in 10.1.NOTE 2In the event that the glass electrode becomes coated with anoil, grease, or other film, it is recommended
45、 thata1to1solvent mix oftoluene and ethyl acetate be used to remove the film.12. Calculations Using Reserve Alkalinity Data12.1 Calculations of percent depletion during simulated oractual coolant service may be obtained by use of the followingequation:Percent depletion 5 100 RA1/C12 RA2/C2!/RA1/C1!#
46、 (1)where:RA1= initial reserve alkalinity,RA2= final reserve alkalinity,C1= initial coolant or additive concentration in percent,andC2= final coolant or additive concentration in percent.NOTE 3In the case of a coolant solution, if the concentration isunknown, it can be determined by appropriate test
47、 methods, such asrefractive index, freezing point, or specific gravity, and by reference toavailable tables. The water content of the coolant solution can bedetermined by Test Method D 1123, and the concentration calculated.12.2 The percent depletion data allows coolant investigatorsto compare, on a
48、n equivalent basis, the reserve alkalinity datafrom a number of identical tests on similar coolants.12.3 In the case of vehicle service tests the percent depletionshould be reported on the basis of some unit of mileage, suchas 10 000 miles. As implied in 5.2, percent depletion of thereserve alkalini
49、ty, although related to coolant durability and thecondition or performance of cooling system, is only a part ofthe coolant evaluation procedure.13. Report13.1 Report the sample description and the reserve alkalin-ity to the nearest 0.1 mL of 0.100 N HCl for the standard10-mL sample. Sample description may vary from a simpleidentification number to a complete history and analysis, suchas that utilized for used coolants from laboratory performanceand vehicle service tests.14. Precision and Bias14.1 RepeatabilityDuplicate results by the same operatorshould not be c
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