1、Designation: D4370 01 (Reapproved 2012)Standard Test Methods forAcid and Base Milliequivalent Content of Electrocoat Bath1This standard is issued under the fixed designation D4370; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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.1. Scope1.1 These test methods cover the determination of acid andbase milliequivalent contents of anodic and cathodic e
3、lectro-coat baths and their ultrafiltrates.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
4、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:2D1193 Specification for Reagent Water3. Summary of Test Methods3.1 Specimens are titrated with standard a
5、cid and alkalisolutions respectively. Alternative procedures are given fordetermining acid and base concentrations potentiometrically orusing a pH meter.4. Significance and Use4.1 The acid and base concentrations are a measurement ofthe titratable acidic and alkaline components in the electrocoatbat
6、hs. These measurements are used for research, production orelectrocoat bath process control.5. Apparatus5.1 Automatic Potentiometric Titrator with Stirrer and Re-corder, any model.5.2 Analytical Balance, with sensitivity of 0.1 mg.5.3 pH Meter, any model.5.4 Glass and Saturated Calomel Electrodes.5.
7、5 Syringes, 5-mL disposable.6. Reagents6.1 Purity 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 specifi
8、cations are available.3Other grades may be used, provided it is ascertained that thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.6.2 Purity of WaterReferences to water shall be under-stood to mean water conforming to Type II of Specifica
9、tionD1193.6.3 Potassium Hydroxide Solution in Methanol, 0.1NPrepare by dissolving 5.6 g of potassium hydroxide (KOH)pellets in 1 L of methanol. Standardize against NIST standardreference material of acid potassium phthalate No. 84 using anautomatic potentiometric titrator4to a given end point or,alt
10、ernatively, to a phenolphthalein end point.6.4 Hydrochloric Acid Solution , 0.1 NPrepare by mixingabout 8.50 mL of concentrated hydrochloric acid (HCl) (1.19sp gr) into a mixture of 600 mL water and 400 mL methanol.Standardize against 0.1 N potassium hydroxide solution (see6.3).6.5 1,3-Propanediol (
11、Propylene Glycol) (PG).6.6 Tetrahydrofuran (THF).6.7 Reference pH Standard SolutionsCommercial stan-dards of pH 4.0, 7.0, and 10.0.1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directresponsibility of Subcom
12、mittee D01.21 on Chemical Analysis of Paints and PaintMaterials.Current edition approved June 1, 2012. Published July 2012. Originally approvedin 1984. Last previous edition approved in 2006 as D4370 01 (2006). DOI:10.1520/D4370-01R12.2For referenced ASTM standards, visit the ASTM website, www.astm.
13、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.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the
14、 testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Svehla, G., Automatic Potentiometric Titra
15、tion, Pergamon Press, 1978, p. 187.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17. Sampling and Sample Preparation7.1 The sample should be obtained while the electrocoatbath is under proper circulation such that a uniform material
16、isobtained. In case of an ultrafiltrate, the material should bethoroughly mixed or stirred prior to sampling to assureuniformity.7.2 After sampling and prior to removing a test specimen, itis mandatory that the samples be shaken or stirred until they arehomogeneous and free of any settled material.
17、This is particu-larly important if there is a delay between sampling the bathand performing the test. The absence of settled material can beascertained visually (in a transparent container) or by insertinga spatula, scraping the bottom of the container, and makingsure that there is no settled matter
18、. The shaking or stirring ofthe samples should be carried out up to the moment of takinga specimen; this Point is Very Important.8. Base Concentration Content8.1 Stir the sample very thoroughly to disperse materialsthat might have settled to the bottom of the container. With theaid of a syringe, wit
19、hdraw approximately 5 mL of the samplequickly, weigh the full syringe to 0.1 mg, and record thisweight as W1. Transfer the entire contents of the syringe into a100-mL beaker. Reweigh the empty syringe to 0.1 mg andrecord as W2. Duplicate the procedure using a second speci-men.8.2 Add approximately 4
20、0 mL of THF/PG 80/20 mixture tothe specimens in the beakers and cover, preferably withaluminum foil, to minimize evaporation of the solvent mixture.NOTE 1In cases where the recommended THF/PG 80/20 mixturecauses precipitation of the material, substitute the same amount of anappropriate solvent or so
21、lvent mixture to a new specimen. The formationof a precipitate during the titration might foul the electrode system andmask potentiometric changes. Other solvents suitable for dilution areacetone, dimethylformamide, toluene, or methanol. Any other solvent orsolvent mixture that does not cause the fo
22、rmation of a precipitatethroughout the titration is suitable. In certain instances it may be necessaryto run a titration blank and to make the appropriate corrections for thesolvent.8.3 Titrate both specimens with 0.1 N HCl solution usingthe automatic potentiometric titrator until an end point “brea
23、k”is reached.4Add approximately 5 mL of additional titrant tocomplete the curve. A typical titration curve is shown in Fig. 1.Record as V1the volume of titrant needed for the end point.NOTE 2If the titration curve does not show an inflection point (endpoint), back titration with 0.1 N KOH will give
24、an acceptable result.9. Base Content Calculation9.1 Calculate the base content as follows:A 5V13 N1!3100W12 W2!Mwhere:A = milliequivalents of base per gram of nonvolatile matter,V1= volume of HCl titrant used, mL,N1= normality of HCl titrant,W1= mass of the syringe filled with sample, mg,W2= mass of
25、 the empty syringe after delivery of the speci-men, mg, andM = nonvolatile matter content, %.10. Acid Concentration Content10.1 Using a fresh portion of the sample, follow 8.1 and 8.2.10.2 Titrate both specimens with 0.1 N KOH solution usingthe automatic potentiometric titrator until an end point br
26、eak isreached.Add about 5 mL more of titrant to complete the curve.From the curve, determine and record, as V2, the volume oftitrant needed for the end point.411. Acid Content Calculation11.1 Calculate the acid content as follows:A 5V23 N2! 3100W32 W4!M(a) Acid Milliequivalent Content Titration(b) B
27、ase Milliequivalent Content TitrationFIG. 1 Potentiometric Titration Curves for the Acid and Base Mil-liequivalent ContentD4370 01 (2012)2where:A = milliequivalents of acid per gram of nonvolatile mat-ter,V2= volume of KOH titrant used, mL,N2= normality of KOH titrant,W3= mass of the syringe filled
28、with sample, mg,W4= mass of the empty syringe after delivery of thespecimen, mg, andM = nonvolatile matter content, %.12. Base Concentration Content Using a pH Meter12.1 Proceed in accordance with 8.1 and 8.2.12.2 Standardize the pH meter at 4.0 and 7.0.12.3 Titrate both specimens with 0.1 N HCl unt
29、il a pH of 4.0is obtained. Make certain that the solutions are well agitatedduring titration (a magnetic stirrer is recommended). Recordvolume of titrant, as V1, used for each titration. Becauseelectrocoating paints vary greatly, it might be advisable totitrate to a pH value agreed upon between the
30、producer and theuser.13. Base Content Calculation13.1 Calculate the base content as described in Section 9.14. Acid Concentration Content Using a pH Meter14.1 Proceed in accordance with 8.1 and 8.2.14.2 Standardize the pH meter at 7.0 and 10.0.14.3 Titrate both specimens with 0.1 N KOH until a pH of
31、10.0 is obtained. Make certain that solutions are well agitatedduring titration (a magnetic stirrer is recommended). Recordvolume of titrant, as V2used for each.15. Acid Content Calculation15.1 Calculate the acid content as described in Section 11.16. Precision and Bias16.1 PrecisionIn an interlabor
32、atory study of the testmethods, in which six laboratories measured in duplicate ontwo days four electrocoat samples with acid and base mil-liequivalents ranging from 0.2 to 0.8, the within-laboratorycoefficient of variation, after discarding one result, was foundto be 1.4 % relative at 23 df and the
33、 between-laboratorycoefficient of variation 5.7 % relative at 19 df. Based on thesecoefficients, the following criteria should be used for judgingthe acceptability of results at the 95 % confidence level:16.1.1 RepeatabilityTwo results, each the mean of dupli-cate determination, obtained by the same
34、 operator on differentdays should be considered suspect if they differ by more than4.1 % relative.16.1.2 ReproducibilityTwo results, each the mean of du-plicate determinations, obtained by operators in different labo-ratories should be considered suspect if they differ by morethan 17 % relative.16.2
35、 BiasBias cannot be determined because there are noaccepted standards for acid or base content of electrocoatbaths.17. Keywords17.1 acid content; base content; electrocoat bathsASTM International takes no position respecting the validity of any patent rights asserted in connection with any item ment
36、ionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee
37、and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting
38、 of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO B
39、ox C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4370 01 (2012)3
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