1、Designation: D 4584 05Standard Test Method forMeasuring Apparent pH of Electrocoat Baths1This standard is issued under the fixed designation D 4584; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numbe
2、r in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the freehydrogen ion concentration of electrocoat baths and theirultrafiltrates.1.2 The values s
3、tated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety
4、 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1293 Test Methods for pH of WaterE70 Test Method for pH of Aqueous Solutions with theGlass ElectrodeE 180 Practice for Dete
5、rmining the Precision Data ofASTM Methods for Analysis and Testing of IndustrialChemicals3. Summary of Test Method3.1 A specimen of a well-agitated electrocoat bath is placedin a stirrer-equipped container and the pH measured with a pHmeter and associated glass and reference electrodes.4. Significan
6、ce and Use4.1 The pH is the measure of the free hydrogen ionconcentration of a sample, and it indicates whether an electro-coat bath is acidic, neutral, or basic. Since pH measurements ofgood precision are made in aqueous solutions, it is suggestedthat the pH measurements of electrocoat baths are on
7、lysemi-quantitative, and therefore such measurements should bereferred to as apparent pH measurements.4.2 The pH of electrocoat paints is used for research,production, and quality control or electrocoat bath processcontrol.4.3 Other related methods for determining the pH of wateror aqueous systems a
8、re described in Test Methods D 1293 andE70.5. Apparatus5.1 pH Meter,5.2 Glass and Reference Electrodes.NOTE 1Due to the polarity of electrocoat materials it is desirable touse a separate set of electrodes for each bath polarity, cathodic and anodic,because a bath of opposite polarity poisons the ele
9、ctrodes. A desiredpractice is to rinse the electrodes after each measurement with anappropriate solvent for the electrocoat material.5.3 Thermometer, capable of 0.5C accuracy with a 2 to32C range.6. Reagents6.1 Reference Standard Solutions, commercial standards ofpH 4.0, 7.0, and 10.0.6.2 Purity of
10、WaterReferences to water shall be under-stood to mean water conforming to Type II of SpecificationD 1193.7. Sampling and Sample Preparation7.1 The sample should be obtained while the electrocoatbath is under proper circulation so that a uniform material isobtained. In case of an ultrafiltrate, the m
11、aterial 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 sample be shaken or stirred until it ishomogeneous and free of any settled material. This is particu-larly important if there is any del
12、ay between the sampling ofthe bath and the preparation of the specimens for the test. Theabsence of settled material can be ascertained visually (in atransparent container) or by inserting a spatula, scraping thebottom of the container to make sure that there is no settled1This test method is under
13、the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, andApplications and is the direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved Jan. 1, 2005. Published February 2005. Originallyapproved in 1986. Last p
14、revious edition approved in 1999 as D 4584 (1999).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.1Copyright
15、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.matter. Shake or stir the samples until specimens are taken formeasurement; this point is very important.8. Procedure8.1 StandardizationTurn on the pH meter and allow it towarm up. Wash the electr
16、odes with a stream of water. Use thepH meter manufacturers instructions to calibrate the elec-trodes with buffer solutions of pH 4 and 7 for cationic systemsand 7 and 10 for anionic systems. Rinsing the electrodesthoroughly after each calibration. The reference buffer solu-tions should thoroughly ma
17、tch the temperature of the samplesto be measured within 2C.8.2 Apparent pH Measurement:8.2.1 Place a suitable quantity of a well-mixed electrocoatspecimen in a clean and dry container equipped with a stirrer(preferably magnetic). Operate the stirrer fast enough to avoidseparation of the paint but sl
18、ow enough to prevent splashing orvortexing. Allow the temperature of the specimen to come toequilibrium (that is, the temperature should show a drift of lessthan 0.5C/min). Record the temperature, and dial in thetemperature correction on the pH meter. Place the electrodes inthe specimen and determin
19、e the pH value in accordance withthe pH meter manufacturers instructions. Record the pH valueand the temperature of the specimen.8.2.2 Run two successive specimens of the electrocoat bathsample; the pH value should be within 0.1 units/min andshould show drifts of less than 0.1 units/min. If these dr
20、iftlimits are not met, check the pH meter and repeat the wholeprocedure.9. Precision and Bias9.1 In an interlaboratory study of the test method, with fivelaboratories measuring five electrocoat bath samples with pHranging from 2.6 to 8.0, the intralaboratory standard deviation(in accordance with Pra
21、ctice E 180) was found to be 0.03 unitsat 25 df, and the interlaboratory coefficient of variation was0.08 units at 20 df. Based on these standard deviations, thefollowing criteria should be used for judging the acceptabilityof results at the 95 % confidence level:9.1.1 RepeatabilityTwo results, each
22、 the mean of dupli-cate determinations, obtained by the same operator on differentdays should be considered suspect if they differ by more than0.1 units.9.1.2 ReproducibilityTwo results, each the mean of dupli-cate determinations, obtained by operators in different labora-tories should be considered
23、 suspect if they differ by more than0.3 units.9.1.3 BiasBias cannot be determined for this methodbecause there are no accepted standards for the free hydrogenion content of electrocoat baths and their ultrafiltrates.10. Keywords10.1 electrocoat baths; pH; pH measurement; ultrafiltratesASTM Internati
24、onal takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin 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 thei
25、r own responsibility.This standard is subject to revision at any time by the responsible technical committee 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 b
26、e addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting 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 Standard
27、s, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box 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).D4584052
