1、Designation: A 630 03 (Reapproved 2009)Standard 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 revisio
2、n, 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.INTRODUCTIONFour test methods for
3、determination of 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
4、by the consumer or 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
5、 Specification A 624/A 624M and Specification A 626/A 626M.1. Scope1.1 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)
6、 10 to 18CSellars Test Method 19 to 28DTitration Test Method 29 to 371.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standar
7、d 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM
8、 Standards:2A 599/A 599M Specification for Tin Mill Products, Electro-lytic Tin-Coated, Cold-Rolled 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-l
9、ytic Tin Plate, Single ReducedA 626/A 626M Specification for Tin Mill Products, Electro-lytic Tin 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
10、the determination of tin coatingweights on steel plate.4. Summary of Test Method4.1 The procedure 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 iodat
11、e-iodide solution isback titrated with standard sodium thiosulfate using a starchindicator.1These 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 Mill Products.Current edition app
12、roved April 1, 2009. Published April 2009. Originallyapproved in 1968. Last previous edition approved in 2003 as A 630 - 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
13、efer 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. Apparatus35.1 The detinning cell consists essentially of two cathodesof carbon rod, the sample that serves as an anode,
14、 and a beakerof dilute hydrochloric 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 sampl
15、e suspendedmidway between the two cathodes. 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 Asource of direct current that can be regulated to supplyup to 3 A at 3 to 5 V through the deplater is required.5.3
16、 Although regular laboratory glassware 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 ir
17、on in the solution adhering to the porouscells 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 bef
18、ore test samples are run.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 Societywhere such specificati
19、ons are available.4Other grades may 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 b
20、yNonreferee Method of Test Methods D 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 1.2
21、1g of NaOH in 1 L of distilled water. 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, heat
22、the flask but do not boil violently. 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 f
23、rom the CO2system and titrate with the 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,
24、 for a 4-in.2(25.81-cm2)sample.6.5 Sodium 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
25、the Bendixapparatus and titrate 20 mL 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
26、 3 17.28,where A = millilitres of sodium 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
27、 litre of distilled water in a light-proofbottle. 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 solutio
28、n.6.7 Starch SolutionHeat 200 mL of distilled 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
29、samples for coating weight determinations areobtained by stamping disks 2.257 6 0.001 in. (57.33 6 0.02mm) in diameter which is equivalent to 4 in.2(25.81 cm2)ofarea (8 in.2(52 cm2) of surface area). Recommended methodsof obtaining representative samples are described in the TinMill Products section
30、s of the American Iron and Steel Insti-tutes Steel Products Manual.58. Procedure8.1 Make required electrical connections.8.2 Add HCl (1+1) to the porous tubes containing thecarbon cathodes.8.3 Suspend the sample disk of tin plate from the magneticholder.3Complete details and drawings of the apparatu
31、s are contained in U. S. PatentNo. 2,455,726 entitled “Method for Electrolytic Stripping and Determination ofPlating Metals.” A suitable commercial supplier of the apparatus has been found tobe the Wilkens-Anderson Company of Chicago.4Reagent Chemicals, American Chemical Society Specifications, Amer
32、icanChemical Society, Washington, DC. For suggestions on the 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. (USP
33、C), Rockville,MD.5Available from American Iron and Steel Institute (AISI), 1140 ConnecticutAve., NW, Suite 705, Washington, DC 20036, http:/www.steel.org.A 630 03 (2009)2NOTE 1If it is desired to strip on one side only, mask the opposite sideand reduce the current to half its normal value. If a heav
34、y oxide film hasdeveloped on the tin plate during storage, the plate must be cathodicallycleaned 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
35、sample and porous cells areimmersed.8.6 Turn on d-c current and adjust to give 0.5 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 bl
36、ue color.8.10 The stripping times and amounts of KIO3-KI solutionto use are as follows: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
37、toremove all of the tin. Results will be high by approximately0.01 lb/bb for each 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
38、, 60.03 lb/bbfor 0.75-lb coatings, and 60.04 lb/bb for 1.25-lb coatings. Datahave 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 tot
39、al tin coating weight but also to determine that part of thetin coating which is 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
40、 thehydrochloric acid. The potential difference developed betweenthe sample and a 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.
41、 1) or a digitalreadout. Since the stripping current has been preset, the free-tinand 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, expre
42、ssing the results asmilligrams or pounds of tin per base box per second.12.2 The 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
43、are two commercially available constant current,electrolytic units that are in common 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, De
44、cember 1959,pp. 1926.7Available from Coulometric Systems, Bergholtz, OH.8Available from Products Distribution Service Division, Wilkens Anderson Co.,4525 West Division St., Chicago, IL 60651.A 630 03 (2009)314.5.1 Tinplate samples for coating weight determinationsare obtained by stamping discs 2.257
45、 6 0.001 in. (57.33 60.02 mm) in diameter. This is equivalent to 4 in.2(25.81 cm2)of 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.
46、6.1 The distance 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
47、of Equipment Operation: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
48、 current (Coulombs) 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
49、 test sample.15.3 Reagent: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 l
