1、Designation: A630 16A630 16aStandard 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
2、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 U.S. Department of Defense.INTRODUCTIONFour test methods for determi
3、nation 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 by the
4、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 for the specific classdesignation are outlined in Specificat
5、ion A624/A624M and Specification A626/A626M.1. Scope1.1 These test methods include four methods for the determination of tin coating weights for electrolytic tin plate as follows:Test Method SectionsABendix Test Method 3 to 9BConstant-Current, Electrolytic Test Method (Referee Method) 10 to 18BConst
6、ant-Current, Electrolytic Test Method (Referee Method) 10 to 17CSellars Test Method 19 to 28CSellars Test Method 18 to 27DTitration Test Method 29 to 37DTitration Test Method 28 to 361.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathema
7、ticalconversions to SI units that are provided for information only and are not considered standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and heal
8、th practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A624/A624M Specification for Tin Mill Products, Electrolytic Tin Plate, Single ReducedA626/A626M Specification for Tin Mill Products, Electrolytic Tin Plate, Double ReducedD1
9、125 Test Methods for Electrical Conductivity and Resistivity of WaterMETHOD ADETERMINATION OF THE TIN COATING WEIGHTS BY THE BENDIX TEST METHOD3. Scope3.1 This test method covers the determination of tin coating weights on steel plate.1 These test methods are under the jurisdiction of ASTM Committee
10、 A01 on Steel, Stainless Steel and Related Alloys and are the direct responsibility of SubcommitteeA01.20 on Tin Mill Products.Current edition approved May 1, 2016Dec. 1, 2016. Published September 2016December 2016. Originally approved in 1968. Last previous edition approved in 20142016as A630 - 03A
11、630 - 16.(2014). DOI: 10.1520/A0630-16.10.1520/A0630-16A.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This
12、 document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior edition
13、s as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*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. U
14、nited States14. Summary of Test Method4.1 The procedure involves dissolution of tin from a tin plate anode in a dilute hydrochloric acid solution containing a measuredexcess of standard potassium iodate-potassium iodide solution. Excess iodine from the iodate-iodide solution is back titrated withsta
15、ndard sodium thiosulfate using a starch indicator.5. Apparatus35.1 The detinning cell consists essentially of two cathodes of carbon rod, the sample that serves as an anode, and a beaker ofdilute hydrochloric acid electrolyte. The carbon rods (6 by 0.25 in. or 152 by 6.35 mm, encased in porous porce
16、lain thimbles) aresuspended from a suitable frame about 1 in. (25 mm) apart. A small glass-enclosed magnet is attached to the frame in such amanner that it will hold the sample suspended midway between the two cathodes. A movable platform permits the beaker ofelectrolyte to be brought up around the
17、assembly so that the sample will be completely immersed.5.2 A source of direct current that can be regulated to supply up to 3 A at 3 to 5 V through the deplater is required.5.3 Although regular laboratory glassware can be used, it is advisable to use automatic dispensing pipets or burets, amotor-dr
18、iven stirrer for titrations, and a timing switch when large numbers of determinations are to be made.5.4 PrecautionsThe apparatus must be kept in continuous operation to prevent iron in the solution adhering to the porous cellsfrom oxidizing and subsequently liberating iodine from the potassium ioda
19、te-potassium iodide solution. If the instrument has beenidle for some time, it is necessary to remove the ferric iron by running a disk of tinplate through the regular procedure before testsamples are run.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless oth
20、erwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society wheresuch specifications are available.4 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highp
21、urity to permit its use without lessening the accuracy of the determination.6.2 WaterDeionized or distilled water having a volume resistivity greater than 1 Mcm at 25C as determined by NonrefereeMethod of Test Methods D1125.6.3 Hydrochloric Acid (1.7 to 2.0 N)Add 1 part of concentrated hydrochloric
22、acid (HCl, sp gr 1.19, 36.5 to 38.0%) to 5 partsof 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 1.21 g ofNaOH in 1 L of distilled water. Standardize as follows: Transfer 0.2700 g of National Bureau of Standards tin
23、to a 500-mLErlenmeyer flask. Add 200 mL of HCl (1+1). Connect the flask to a carbon dioxide (CO2) system and displace the air in the flaskwith CO2. While continuing the flow of CO2, heat the flask but do not boil violently. After the tin has dissolved add 0.5 g ofantimony and 2 g of high-purity alum
24、inum. Heat until the aluminum is completely dissolved and digest for an additional 10 min.Cool the flask to room temperature in running water while maintaining an atmosphere of CO2. Disconnect from the CO2 systemand titrate with the KIO3-KI solution using starch as an indicator. Calculate the tin ti
25、ter, 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 coatings over 0.50 lb/bb
26、)Dissolve 15.11 g of Na2S2O35 H2O and 1.11 g ofNaOH in 1 litre of distilled water in a light-proof bottle. Allow this solution to age for 72 h, remix, and standardize as follows:Connect the bottle to the Bendix apparatus and titrate 20 mL of the standardized KIO3-KI solution with the thiosulfate sol
27、utionusing the same procedure as is used for making weight of coating determinations, but ignore the stripping unit. The tin equivalentof the Na2S2O3 solution in pounds per base box is equal to: 20/A T 17.28, where A = millilitres of sodium thiosulfate solutionused in titrating 20 mL of standard KIO
28、3-KI solution. A chart can be prepared showing lb/bb/mL of thiosulfate.6.6 Sodium Thiosulfate, Standard Solution (for coatings 0.50 lb/bb and under)Dissolve 6.57 g of Na2S2O35 H2O and 2.78g of NaOH in 1 litre of distilled water in a light-proof bottle. Larger quantities in the same proportions may b
29、e prepared if desired.3 Complete details and drawings of the apparatus are contained in U. S. Patent No. 2,455,726 entitled “Method for Electrolytic Stripping and Determination of PlatingMetals.” A suitable commercial supplier of the apparatus has been found to be the Wilkens-Anderson Company of Chi
30、cago.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Ph
31、armacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.A630 16a2Allow that solution to age for 72 h, remix, and standardize by the same procedure used for the stronger Na2S2O3 solution but useonly 10 mL of potassium iodate-potassium iodide solution.6.7 Starch Sol
32、utionHeat 200 mL of distilled water to boiling in a Florence flask and slowly add 2.5 g of soluble starch pastewhile the solution is agitated. Add the hot starch solution to 500 mL of distilled water containing 2.5 g of NaOH. Dilute to 1 Land thoroughly mix.7. Test Sample7.1 Tin plate samples for co
33、ating weight determinations are obtained by stamping disks 2.257 6 0.001 in. (57.33 6 0.02 mm)in diameter which is equivalent to 4 in.2 (25.81 cm2) of area (8 in.2 (52 cm2) of surface area). Recommended methods of obtainingrepresentative samples are described in the Tin Mill Products sections of the
34、 American Iron and Steel Institutes Steel ProductsManual.58. Procedure8.1 Make required electrical connections.8.2 Add HCl (1+1) to the porous tubes containing the carbon cathodes.8.3 Suspend the sample disk of tin plate from the magnetic holder.NOTE 1If it is desired to strip on one side only, mask
35、 the opposite side and reduce the current to half its normal value. If a heavy oxide film hasdeveloped on the tin plate during storage, the plate must be cathodically cleaned prior to testing.8.4 Place a measured quantity of standardized KIO3-KI solution into a 400-mL beaker (see 8.10). Simultaneous
36、ly add 250 mLof dilute HCl and mix thoroughly.8.5 Raise the beaker so that the sample and porous cells are immersed.8.6 Turn on d-c current and adjust to give 0.5 A/in.2 of sample.8.7 Time for complete removal of tin (see 8.10).8.8 Remove the beaker and add approximately 5 mL of starch indicator sol
37、ution.8.9 Titrate with standardized Na2S2O3 solution to the disappearance of the blue color.8.10 The stripping times and amounts of KIO3-KI solution to use are as follows:Amount ofStripping KIO3-KIProduct Time, s Solution, mLElectrolytic 100 90 20Electrolytic 75 75 20Electrolytic 50 60 10Electrolyti
38、c 25 60 10Electrolytic 10 45 10Stripping time should not be longer than is required to remove all of the tin. Results will be high by approximately 0.01 lb/bbfor each minute of over-stripping.9. Reproducibility of Results9.1 Arbitrary maximum spreads in intermill check tests show the reproducibility
39、 of test results by the Bendix Method to be asfollows: 60.02 lb/bb for 0.25lb coatings, 60.03 lb/bb for 0.75-lb coatings, and 60.04 lb/bb for 1.25-lb coatings. Data have notbeen developed for 0.10-lb coatings.METHOD BDETERMINATION OF THE TIN COATING WEIGHTS BY THE CONSTANT CURRENT,ELECTROLYTIC METHO
40、D (REFEREE METHOD)10. Scope10.1 This test method6 may be used to determine not only the total tin coating weight but also to determine that part of the tincoating which is present as free tin and that part which is present in the alloyed form.11. Summary of Test Method11.1 In this test method, the t
41、in is stripped from a sample of tin-plate anodically at constant current in an electrolyte of thehydrochloric acid. The potential difference developed between the sample and a reference electrode is plotted against time on a5 Available from American Iron and Steel Institute (AISI), 1140 Connecticut
42、Ave., NW, Suite 705, Washington, DC 20036, http:/www.steel.org.6 See Kunze, C. T., and Willey, A. R., “Electrolytic Determination of Tin and Tin-Iron Alloy Coating Weights on Tin Plate,” Journal, Electrochemical Society, Vol 99,No. 9, September 1952, pp. 354359; and “Methods for Determination of Coa
43、ting Weights of Tin Plate,” American Iron and Steel Institute, December 1959, pp. 1926.A630 16a3strip chart recorder or an electric digital readout. The time required for stripping the free tin and alloyed tin, respectively, are readfrom the resulting chart (see Fig. 1) or a digital readout. Since t
44、he stripping current has been preset, the free-tin and alloy-tincoating weights are calculated by employing Faradays law of electrolysis.12. Calibration and Standardization12.1 Determine the weight loss of pure tin specimens electrolyzed for a given time interval, expressing the results as milligram
45、sor pounds of tin per base box per second.12.2 The test specimen should be a 4-in.2 disk of pure tin approximately 0.20 in. (5.1 mm) thick.12.3 The milliammeter should be frequently checked using a precision milliammeter.13. Available Constant Current Procedures13.1 There are twothree commercially a
46、vailable constant current, electrolytic units that are in common use. Either of thefollowing, or equivalent equipment, can be used as an acceptable referee method:13.1.1 Willey “r” is the interval representing the critical difference between two test results for the same material, obtained by the sa
47、meoperator using the same equipment on the same day in the same laboratory.EReproducibility Limit (R) The maximum 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 16a8NOTE
48、3The ideal concentration is one that gives a numerical value of 0.005786 g of Sn/mL of solution. Values between 0.00577 and 0.00580 areconsidered acceptable; otherwise, the concentration should be adjusted. Using a solution of the concentration indicated, 1 mL of solution corresponds toa coating wei
49、ght of 0.1000 lb Sn/bb (1.121 g Sn/m2) of surface when using 4 in.2 (25.81 cm2) of tinplate as the sample.23.5 Starch SolutionDissolve 2.5 g of NaOH in 500 mL of water. Place about 200 mL of water in a Florence flask and bringit to a boil. Add 2.5 g of soluble starch to 10 mL of water and stir to make a smooth paste. Then add this paste cautiously to theboiling water. Remove this solution from the source of heat and shake gently. Pour the starch dispersion into the NaOH solution,dilute to 1 litre, and mix thoroughly.24. Test Specimens or Sa
