1、Designation: A630 16a1Standard Test Methods forDetermination of Tin Coating Weights for Electrolytic TinPlate1This standard is issued under the fixed designation A630; 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 () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1NOTEA Summary of Changes was added editorially
3、 in January 2017.INTRODUCTIONFour test methods for 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 fl
4、uorescence measurementsystems for control purposes by the consumer or supplier. However, in case of dispute, the refereemethod is to be used to determine conformance to Specification A624/A624M and SpecificationA626/A626M.Sampling procedures for tin coating-weight testing and applicable standards fo
5、r the specific classdesignation are outlined in Specification A624/A624M and Specification A626/A626M.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-Curren
6、t, Electrolytic Test Method (Referee Method) 10 to 17CSellars Test Method 18 to 27DTitration Test Method 28 to 361.2 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
7、are not considered standard.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 and health practices and determine the applica-bility of regulatory limitations
8、prior to use.2. Referenced Documents2.1 ASTM Standards:2A624/A624M Specification for Tin Mill Products, Electro-lytic Tin Plate, Single ReducedA626/A626M Specification for Tin Mill Products, Electro-lytic Tin Plate, Double ReducedD1125 Test Methods for Electrical Conductivity and Resis-tivity of Wat
9、erMETHOD 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 involves dissolution of tin from a tinplate anode in a dilute hydrochloric acid solution con
10、taining a1These 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 approved Dec. 1, 2016. Published December 2016. Originallyapproved in 1968. Last prev
11、ious edition approved in 2016 as A630 - 16. DOI:10.1520/A0630-16AE01.2For 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
12、website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardizat
13、ion established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1measured excess of standard potassium iodate-potassium io-dide solution. Excess iodine from the
14、iodate-iodide solution isback titrated with standard sodium thiosulfate using a starchindicator.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 acid electrolyte. The carbon rods (6 by0.25 in
15、. or 152 by 6.35 mm, encased in porous porcelainthimbles) are suspended from a suitable frame about 1 in.(25 mm) apart. A small glass-enclosed magnet is attached tothe frame in such a manner that it will hold the samplesuspended midway between the two cathodes. A movableplatform permits the beaker o
16、f electrolyte to be brought uparound the assembly so that the sample will be completelyimmersed.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 Although regular laboratory glassware can be used, it isadvisable to use automatic d
17、ispensing 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 porouscells from oxidizing and subsequently libera
18、ting 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. Reagents6.1 Purity of ReagentsReagent grade chemicals sha
19、ll 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 beused, provided it is first ascertained that the
20、 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 Mcm at 25C as determined byNonreferee Method of Test Methods D1125.6.3 Hydrochloric Acid (1.7 to 2.0 N)Add 1 par
21、t 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. Standardize as follows:Transfer 0.2700 g of Natio
22、nal 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. After the tin has dissolvedadd 0.5 g of antimony a
23、nd2gofhigh-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 the KIO3-KIsolution using starch as an indicator. Ca
24、lculate 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.2(25.81-cm2)sample.6.5 Sodium Thiosulfate, Standard Solution (for coatingso
25、ver 0.50 lb/bb)Dissolve 15.11 g of Na2S2O35 H2O and 1.11g of NaOH in 1 litre of distilled water in a light-proof bottle.Allow this solution to age for 72 h, remix, and standardize asfollows: Connect the bottle to the Bendix apparatus and titrate20 mL of the standardized KIO3-KI solution with the thi
26、osul-fate solution using the same procedure as is used for makingweight of coating determinations, but ignore the stripping unit.The tin equivalent of the Na2S2O3solution in pounds per basebox is equal to: 20/AT17.28, where A = millilitres ofsodium thiosulfate solution used in titrating 20 mL of sta
27、ndardKIO3-KI solution. A chart can be prepared showing lb/bb/mLof 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-proofbottle. Larger quantities in the same proportions
28、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 distilled water toboiling in a Florence flask and slowly
29、 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 determinations areobtained by stamping disks 2.257 6 0.001 in. (5
30、7.33 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 Tin3Complete details and drawings of the apparatus are contained in U. S. PatentNo. 2,455,726 entitled “Method for E
31、lectrolytic 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, AmericanChemical Society, Washington, DC. For suggestions on the testin
32、g 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.A630 16a12Mill Products sections of the American I
33、ron 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.NOTE 1If it is desired to strip on one side only, mask the opposi
34、te 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 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 o
35、f 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 0.5 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
36、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 follows:Amount ofStripping KIO3-KIProduct Time, s Solution, mLElectrolytic 100 90 20Electrolytic 75 75 20Electrolytic 50 60 10Electrolytic 25 60 10Electroly
37、tic 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 minute of over-stripping.9. Reproducibility of Results9.1 Arbitrary maximum spreads in intermill check testsshow the reproducibility of test results by t
38、he 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 not been developed for 0.10-lb coatings.METHOD BDETERMINATION OF THE TINCOATING WEIGHTS BY THE CONSTANTCURRENT, ELECTROLYTIC METHOD (REFEREEMETHOD)10. Sc
39、ope10.1 This test method6may be used to determine not onlythe total tin coating weight but also to determine that part of thetin coating which is 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 sampl
40、e oftin-plate anodically at constant current in an electrolyte of 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 allo
41、yed tin, respectively,are read from the resulting chart (see Fig. 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 o
42、f pure tin specimenselectrolyzed for a given time interval, expressing 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
43、milliammeter.13. Available Constant Current Procedures13.1 There are three commercially available constantcurrent, 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 ofC
44、oating Weights of Tin Plate,” American Iron and Steel Institute, December 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.A630 16a1313.1.3 The Donart Test MethodSup
45、plier will providesetup, start, and running procedures.914. Willey “r” is the interval representing the critical difference between two test results for the same material, obtained by the sameoperator using the same equipment on the same day in the same laboratory.EReproducibility Limit (R) The maxi
46、mum difference between two results, obtained under reproducibility conditions, that is accepted as plausible due to random causesunder normal and correct operation of the test.A630 16a1619.2 The tin is titrated with a standard iodide-iodatesolution, using starch as an indicator.20. Significance and
47、Use20.1 This test method covers determination of the total tin inthe sample tested and does not apportion the tin to one or theother side of the test specimen. The calculations appearing inSection 27 assume uniform distribution of tin over the twosurfaces.20.2 This test method does not differentiate
48、 between free tinon the tinplate surface, tin combined with iron in the interme-diate alloy layer, or tin alloyed with the steel as a residualtramp element.21. Interferences21.1 This test method relies on a redox reaction. Therefore,any contaminant that may be reduced by the nascent hydrogenliberate
49、d as the sample dissolves in hydrochloric acid and maybe subsequently oxidized by the KI-KIO3titrant, must beavoided. The chromate treatments commonly applied to tin-plate have not been found to cause significant errors.22. Apparatus22.1 Reaction Vessel,11such as a 500 mL Erlenmeyer flask,closed with a two-hole stopper. One opening in the stoppershall be connected to a source of carbon dioxide (CO2) gas, theother, allowing escape of the hydrogen, displaced air, CO2, andacid vapors shall be connected to a water trap. This will scrubthe hydrochlor
