ASTM_D_1121_-_11.pdf

Designation:D112111Standard Test Method forReserve Alkalinity of Engine Coolants and Antirusts1This standard is issued under the fixed designation D1121;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()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 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 address 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:2D1123 Test Methods for Water in Engine Coolant Concen-trate by the Karl Fischer Reagent MethodD1176 Practice for Sampling and Preparing Aqueous Solu-tions of Engine Coolants orAntirusts for Testing PurposesD1287 Test Method for pH of Engine Coolants andAntirusts3.Terminology3.1 Definitions:3.1.1 reserve 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 diluted 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 thereserve 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 unused 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 solutions,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 D15 on Engine 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 mLof concentrated coolant to a pH of 5.5.The 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 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 of 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 Related Fluids and is the direct responsibility of SubcommitteeD15.04 on Chemical Properties.Current edition approved Oct.1,2011.Published October 2011.Originallyapproved in 1950.Last previous edition approved in 2007 as D1121 07.DOI:10.1520/D1121-11.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.5 Generally,most metals in an automotive cooling systemcorrode less 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 in