1、Designation: A 630 03Standard Test Methods forDetermination of Tin Coating Weights for Electrolytic TinPlate1This standard is issued under the fixed designation A 630; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. 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.INTRODUCTIONFour test methods for determination of
3、tin coating weights are described. These are typical methodsand represent those most commonly used in the tin plate industry. Publication of these test methodsis not intended to preclude the use of any other methods such as X-ray fluorescence measurementsystems for control purposes by the consumer o
4、r supplier. However, in case of dispute, the refereemethod is to be used to determine conformance to Specification A 624/A 624M and SpecificationA 626/A 626M.Sampling procedures for tin coating-weight testing and applicable standards for the specific classdesignation are outlined in Specification A
5、624/A 624M and Specification A 626/A 626M.1. Scope*1.1 These test methods include four methods for the deter-mination of tin coating weights for electrolytic tin plate asfollows:Test Method SectionsABendix Test Method 3 to 9BConstant-Current, Electrolytic Test Method (Referee Method) 10 to 18CSellar
6、s Test Method 19 to 28DTitration Test Method 29 to 371.2 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is th
7、eresponsibility 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:2A 599/A 599M Specification for Tin Mill Products, Elec-trolytic Tin-Coated, Cold-Rolle
8、d SheetA 623 Specification for Tin Mill Products, General Require-mentsA 623M Specification for Tin Mill Products, General Re-quirements MetricA 624/A 624M Specification for Tin Mill Products, Electro-lytic Tin Plate, Single ReducedA 626/A 626M Specification for Tin Mill Products, Electro-lytic Tin
9、Plate, Double ReducedD 1125 Test Methods for Electrical Conductivity and Re-sistivity of WaterMETHOD ADETERMINATION OF THE TINCOATING WEIGHTS BY THE BENDIX TESTMETHOD3. Scope3.1 This test method covers the determination of tin coatingweights on steel plate.4. Summary of Test Method4.1 The procedure
10、involves dissolution of tin from a tinplate anode in a dilute hydrochloric acid solution containing ameasured excess of standard potassium iodate-potassium io-dide solution. Excess iodine from the iodate-iodide solution isback titrated with standard sodium thiosulfate using a starchindicator.1These
11、test methods are under the jurisdiction of ASTM Committee A01 onSteel, Stainless Steel and Related Alloys and are the direct responsibility ofSubcommittee A01.20 on Tin Plate.Current edition approved November 1, 2003. Published January 2004. Originallyapproved in 1968. Last previous edition approved
12、 in 1998 as A 630 - 98.2For 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.1*A Summary of Changes section appears
13、 at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Apparatus35.1 The detinning cell consists essentially of two cathodesof carbon rod, the sample that serves as an anode, and a beakerof dilute hydrochloric
14、 acid electrolyte. The carbon rods (6 by0.25 in. or 152 by 6.35 mm, encased in porous porcelainthimbles) are suspended from a suitable frame about 1 in. 25mm apart. A small glass-enclosed magnet is attached to theframe in such a manner that it will hold the sample suspendedmidway between the two cat
15、hodes. A movable platform per-mits the beaker of electrolyte to be brought up around theassembly so that the sample will be completely immersed.5.2 A source of direct current that can be regulated to supplyup to 3 A at 3 to 5 V through the deplater is required.5.3 Although regular laboratory glasswa
16、re can be used, it isadvisable to use automatic dispensing pipets or burets, amotor-driven stirrer for titrations, and a timing switch whenlarge numbers of determinations are to be made.5.4 PrecautionsThe apparatus must be kept in continuousoperation to prevent iron in the solution adhering to the p
17、orouscells from oxidizing and subsequently liberating iodine fromthe potassium iodate-potassium iodide solution. If the instru-ment has been idle for some time, it is necessary to remove theferric iron by running a disk of tinplate through the regularprocedure before test samples are run.6. Reagents
18、6.1 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 Societywhere such specifications are available.4Other grades may
19、beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 WaterDeionized or distilled water having a volumeresistivity greater than 1 MVcm at 25C as determined byNonreferee Method of Test Methods D
20、 1125.6.3 Hydrochloric Acid (1.7 to 2.0 N)Add 1 part ofconcentrated hydrochloric acid (HCl, sp gr 1.19, 36.5 to38.0%) to 5 parts of water and mix well.6.4 Potassium Iodate-Potassium Iodide, Standard Solution(0.0975 N)Dissolve 3.48 g of KIO3, 21.74 g of KI, and 1.21g of NaOH in 1 L of distilled water
21、. Standardize as follows:Transfer 0.2700 g of National Bureau of Standards tin to a500-mL Erlenmeyer flask. Add 200 mL of HCl (1+1). Connectthe flask to a carbon dioxide (CO2) system and displace the airin the flask with CO2. While continuing the flow of CO2, heatthe flask but do not boil violently.
22、 After the tin has dissolvedadd 0.5 g of antimony and2gofhigh-purity aluminum. Heatuntil the aluminum is completely dissolved and digest for anadditional 10 min. Cool the flask to room temperature inrunning water while maintaining an atmosphere of CO2.Disconnect from the CO2system and titrate with t
23、he KIO3-KIsolution using starch as an indicator. Calculate the tin titer, T,as follows:T 5 A/Bwhere:A = tin used (0.2700 g),B = KIO3-KI solution used for titration, mL, andT = tin titer for above KIO3-KI solution, (grams of tin/mL),T = 17.28 = lb/base box (bb)/mL, for a 4-in.225.81-cm2sample.6.5 Sod
24、ium Thiosulfate, Standard Solution (for coatingsover 0.50 lb/bb)Dissolve 15.11 g of Na2S2O35 H2O and1.11 g of NaOH in 1 litre of distilled water in a light-proofbottle. Allow this solution to age for 72 h, remix, andstandardize as follows: Connect the bottle to the Bendixapparatus and titrate 20 mL
25、of the standardized KIO3-KIsolution with the thiosulfate solution using the same procedureas is used for making weight of coating determinations, butignore the stripping unit. The tin equivalent of the Na2S2O3solution in pounds per base box is equal to: 20/A 3 T 3 17.28,where A = millilitres of sodi
26、um thiosulfate solution used intitrating 20 mL of standard KIO3-KI solution. A chart can beprepared showing lb/bb/mL of thiosulfate.6.6 Sodium Thiosulfate, Standard Solution (for coatings0.50 lb/bb and under)Dissolve 6.57 g of Na2S2O35 H2O and2.78 g of NaOH in 1 litre of distilled water in a light-p
27、roofbottle. Larger quantities in the same proportions may beprepared if desired. Allow that solution to age for 72 h, remix,and standardize by the same procedure used for the strongerNa2S2O3solution but use only 10 mL of potassium iodate-potassium iodide solution.6.7 Starch SolutionHeat 200 mL of di
28、stilled water toboiling in a Florence flask and slowly add 2.5 g of solublestarch paste while the solution is agitated. Add the hot starchsolution to 500 mL of distilled water containing 2.5 g ofNaOH. Dilute to 1 L and thoroughly mix.7. Test Sample7.1 Tin plate samples for coating weight determinati
29、ons areobtained by stamping disks 2.257 6 0.001 in. 57.33 6 0.02mm in diameter which is equivalent to 4 in.225.81 cm2ofarea (8 in.252 cm2 of surface area). Recommended methodsof obtaining representative samples are described in the TinMill Products sections of the American Iron and Steel Insti-tutes
30、 Steel Products Manual.58. Procedure8.1 Make required electrical connections.8.2 Add HCl (1+1) to the porous tubes containing thecarbon cathodes.3Complete details and drawings of the apparatus are contained in U. S. PatentNo. 2,455,726 entitled “Method for Electrolytic Stripping and Determination of
31、Plating Metals.” A suitable commercial supplier of the apparatus has been found tobe the Wilkens-Anderson Company of Chicago.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Ch
32、emical 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.5Available from American Iron and Steel Institute (AISI), 1101 17th St., NW,Suite 1300, Wash
33、ington, DC 20036.A6300328.3 Suspend the sample disk of tin plate from the magneticholder.NOTE 1If it is desired to strip on one side only, mask the opposite sideand reduce the current to half its normal value. If a heavy oxide film hasdeveloped on the tin plate during storage, the plate must be cath
34、odicallycleaned prior to testing.8.4 Place a measured quantity of standardized KIO3-KIsolution into a 400-mL beaker (see 8.10). Simultaneously add250 mL of dilute HCl and mix thoroughly.8.5 Raise the beaker so that the sample and porous cells areimmersed.8.6 Turn on d-c current and adjust to give 0.
35、5 A/in.2ofsample.8.7 Time for complete removal of tin (see 8.10).8.8 Remove the beaker and add approximately 5 mL ofstarch indicator solution.8.9 Titrate with standardized Na2S2O3solution to the dis-appearance of the blue color.8.10 The stripping times and amounts of KIO3-KI solutionto use are as fo
36、llows:Amount ofStripping KIO3-KIProduct Time, s Solution, mLElectrolytic 100 90 20Electrolytic 75 75 20Electrolytic 50 60 10Electrolytic 25 60 10Electrolytic 10 45 10Stripping time should not be longer than is required toremove all of the tin. Results will be high by approximately0.01 lb/bb for each
37、 minute of over-stripping.9. Reproducibility of Results9.1 Arbitrary maximum spreads in intermill check testsshow the reproducibility of test results by the Bendix Methodto be as follows: 60.02 lb/bb for 0.25lb coatings, 60.03 lb/bbfor 0.75-lb coatings, and 60.04 lb/bb for 1.25-lb coatings. Datahave
38、 not been developed for 0.10-lb coatings.METHOD BDETERMINATION OF THE TINCOATING WEIGHTS BY THE CONSTANTCURRENT, ELECTROLYTIC METHOD (REFEREEMETHOD)10. Scope10.1 This test method6may be used to determine not onlythe total tin coating weight but also to determine that part of thetin coating which is
39、present as free tin and that part which ispresent in the alloyed form.11. Summary of Test Method11.1 In this test method, the tin is stripped from a sample oftin-plate anodically at constant current in an electrolyte of thehydrochloric acid. The potential difference developed betweenthe sample and a
40、 reference electrode is plotted against time ona strip chart recorder or an electric digital readout. The timerequired for stripping the free tin and alloyed tin, respectively,are read from the resulting chart (see Fig. 1) or a digitalreadout. Since the stripping current has been preset, the free-ti
41、nand alloy-tin coating weights are calculated by employingFaradays law of electrolysis.12. Calibration and Standardization12.1 Determine the weight loss of pure tin specimenselectrolyzed for a given time interval, expressing the results asmilligrams or pounds of tin per base box per second.12.2 The
42、test specimen should be a 4-in.2disk of pure tinapproximately 0.20 in. 5.1 mm thick.12.3 The milliammeter should be frequently checked usinga precision milliammeter.13. Available Constant Current Procedures13.1 There are two commercially available constant current,electrolytic units that are in comm
43、on use. Either of thefollowing, or equivalent equipment, can be used as an accept-able referee method:13.1.1 Willey and “Methods for Determination ofCoating Weights of Tin Plate,” American Iron and Steel Institute, December 1959,pp. 1926.7Available from Coulometric Systems, Bergholtz, OH.8Available
44、from Products Distribution Service Division, Wilkens Anderson Co.,4525 West Division St., Chicago, IL 60651.A63003314.4 Reagents:14.4.1 Electrolyte1.0 N hydrochloric acid (HCl).14.5 Sample Size:14.5.1 Tinplate samples for coating weight determinationsare obtained by stamping discs 2.257 6 0.001 in.
45、57.33 60.02 mm in diameter. This is equivalent to 4 in.225.81 cm2of area of one side. Sampling procedures for tin coating weighttesting and applicable standards for the specific class designa-tion are outlined in Specifications, A 624, A 624M, A 626, andA 626M.14.6 Interferences:14.6.1 The distance
46、of the cathode from the sample isimportant and should be 0.75 6 0.25 in. 1.90 6 0.64 cm.Also, it is important that the cathode be approximately thesame shape as the sample so that all parts of the anode areequidistant from the cathode.15. The Stannomatic Test Method15.1 Principle of Equipment Operat
47、ion:15.1.1 The free tin and the alloy tin covering the surface ofthe tin plate to be examined are dissolved electrolytically. Thetest size is exactly defined on both sides of the sample by twoprecision gaskets. The free tin and iron-tin alloy results are afunction of the amount of current (Coulombs)
48、 used for strip-ping and are displayed on a numeric readout.15.2 Apparatus:15.2.1 This instrument consists of a stripping cell with astandardized sample size control. The stripping controller has anumeric readout which displays separately free tin and alloy tinon both sides of the test sample.15.3 R
49、eagent:15.3.1 ElectrolyteAs specified by equipment manufac-turer.15.4 Sample Size:15.4.1 Tinplate samples can be of various dimensions butmust be large enough to afford a test area at least 112 in. indiameter. The test area must be reasonably flat. Samplingprocedures for tin coating weight testing and applicable stan-dards for the specific class designations are outlined in Speci-fications A 624/A 624M and A 626/A 626M.15.5 Preparing Sample:15.5.1 The surface of the tested sample shall be clean. Oil,grease and organic coating such as lacqu
