ASTM A630-03(2009)
(Test Method)Standard Test Methods for Determination of Tin Coating Weights for Electrolytic Tin Plate
Standard Test Methods for Determination of Tin Coating Weights for Electrolytic Tin Plate
SIGNIFICANCE AND USE
This test method covers determination of the total tin in the sample tested and does not apportion the tin to one or the other side of the test specimen. The calculations appearing in Section 27 assume uniform distribution of tin over the two surfaces.
This test method does not differentiate between free tin on the tinplate surface, tin combined with iron in the intermediate alloy layer, or tin alloyed with the steel as a residual tramp element.
SCOPE
1.1 These test methods include four methods for the determination of tin coating weights for electrolytic tin plate as follows:
Test Method
Sections
A—Bendix Test Method
3 to 9
B—Constant-Current, Electrolytic Test Method (Referee Method)
10 to 18
C—Sellar's Test Method
19 to 28
D—Titration Test Method
29 to 37
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions 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 responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
3.1 This test method covers the determination of tin coating weights on steel plate.
10.1 This test method may be used to determine not only the total tin coating weight but also to determine that part of the tin coating which is present as free tin and that part which is present in the alloyed form.
19.1 This test method covers the determination of the total weight of tin carried by a unit area of tinplate.
29.1 This test method is normally applicable to the determination of tin coating weights in the range of 0.50 to 1.50 lb of tin/bb.
Note 4—For the determination of the coating weights outside of this range, an iodate solution of appropriate concentration should be prepared so that suitable titrant volumes are obtained. For the determination of low tin coating mass in the range from 0.05–0.49 lb/bb, the number of sample specimens should be adjusted appropriately to maintain a minimum total tin mass equivalent to that present on a 0.50 lb/bb specimen. This test method cannot be used to test single spot tin mass for low tin coating material.
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Designation: A630 − 03(Reapproved 2009)
Standard Test Methods for
Determination of Tin Coating Weights for Electrolytic Tin
Plate
This standard is issued under the fixed designation A630; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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.
INTRODUCTION
Four test methods for determination of tin coating weights are described.These are typical methods
and represent those most commonly used in the tin plate industry. Publication of these test methods
is not intended to preclude the use of any other methods such as X-ray fluorescence measurement
systems for control purposes by the consumer or supplier. However, in case of dispute, the referee
method is to be used to determine conformance to Specification A624/A624M and Specification
A626/A626M.
Sampling procedures for tin coating-weight testing and applicable standards for the specific class
designation are outlined in Specification A624/A624M and Specification A626/A626M.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods include four methods for the deter-
A599/A599M Specification for Tin Mill Products, Electro-
mination of tin coating weights for electrolytic tin plate as
lytic Tin-Coated, Cold-Rolled Sheet
follows:
A623 Specification for Tin Mill Products, General Require-
Test Method Sections
A—Bendix Test Method 3 to 9 ments
B—Constant-Current, Electrolytic Test Method (Referee Method) 10 to 18
A623M Specification for Tin Mill Products, General Re-
C—Sellar’s Test Method 19 to 28
quirements [Metric]
D—Titration Test Method 29 to 37
A624/A624M Specification for Tin Mill Products, Electro-
lytic Tin Plate, Single Reduced
1.2 The values stated in inch-pound units are to be regarded
A626/A626M Specification for Tin Mill Products, Electro-
as standard. The values given in parentheses are mathematical
lytic Tin Plate, Double Reduced
conversions to SI units that are provided for information only
D1125 Test Methods for Electrical Conductivity and Resis-
and are not considered standard.
tivity of Water
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
METHOD A—DETERMINATION OF THE TIN
responsibility of the user of this standard to establish appro-
COATING WEIGHTS BY THE BENDIX TEST
priate safety and health practices and determine the applica-
METHOD
bility of regulatory limitations prior to use.
3. Scope
3.1 This test method covers the determination of tin coating
weights on steel plate.
These test methods are under the jurisdiction of ASTM Committee A01 on
Steel, Stainless Steel and Related Alloysand are the direct responsibility of
Subcommittee A01.20 on Tin Mill Products. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2009. Published April 2009. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1968. Last previous edition approved in 2003 as A630 - 03. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/A0630-03R09. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A630 − 03 (2009)
4. Summary of Test Method 6.3 Hydrochloric Acid (1.7 to 2.0 N)—Add 1 part of
concentrated hydrochloric acid (HCl, sp gr 1.19, 36.5 to
4.1 The procedure involves dissolution of tin from a tin
38.0%) to 5 parts of water and mix well.
plate anode in a dilute hydrochloric acid solution containing a
6.4 Potassium Iodate-Potassium Iodide, Standard Solution
measured excess of standard potassium iodate-potassium io-
(0.0975 N)—Dissolve 3.48 g of KIO , 21.74 g of KI, and 1.21
dide solution. Excess iodine from the iodate-iodide solution is
g of NaOH in 1 L of distilled water. Standardize as follows:
back titrated with standard sodium thiosulfate using a starch
Transfer 0.2700 g of National Bureau of Standards tin to a
indicator.
500-mLErlenmeyer flask.Add 200 mLof HCl (1+1). Connect
the flask to a carbon dioxide (CO ) system and displace the air
5. Apparatus
in the flask with CO . While continuing the flow of CO , heat
2 2
5.1 The detinning cell consists essentially of two cathodes
the flask but do not boil violently. After the tin has dissolved
of carbon rod, the sample that serves as an anode, and a beaker
add 0.5 g of antimony and2gof high-purity aluminum. Heat
of dilute hydrochloric acid electrolyte. The carbon rods (6 by
until the aluminum is completely dissolved and digest for an
0.25 in. or 152 by 6.35 mm, encased in porous porcelain
additional 10 min. Cool the flask to room temperature in
thimbles) are suspended from a suitable frame about 1 in. (25
running water while maintaining an atmosphere of CO .
mm) apart. A small glass-enclosed magnet is attached to the
Disconnect from the CO system and titrate with the KIO -KI
2 3
frame in such a manner that it will hold the sample suspended
solution using starch as an indicator. Calculate the tin titer, T,
midway between the two cathodes. A movable platform per-
as follows:
mits the beaker of electrolyte to be brought up around the
T 5 A/B
assembly so that the sample will be completely immersed.
where:
5.2 Asourceofdirectcurrentthatcanberegulatedtosupply
A = tin used (0.2700 g),
up to 3 A at 3 to 5 V through the deplater is required.
B = KIO -KI solution used for titration, mL, and
5.3 Although regular laboratory glassware can be used, it is
T = tin titer for above KIO -KI solution, (grams of tin/mL),
2 2
advisable to use automatic dispensing pipets or burets, a
T = 17.28 = lb/base box (bb)/mL, for a 4-in. (25.81-cm )
motor-driven stirrer for titrations, and a timing switch when
sample.
large numbers of determinations are to be made.
6.5 Sodium Thiosulfate, Standard Solution (for coatings
5.4 Precautions—The apparatus must be kept in continuous
over 0.50 lb/bb)—Dissolve15.11gofNa S O ·5H Oand1.11
2 2 3 2
operation to prevent iron in the solution adhering to the porous
g of NaOH in 1 litre of distilled water in a light-proof bottle.
cells from oxidizing and subsequently liberating iodine from
Allow this solution to age for 72 h, remix, and standardize as
the potassium iodate-potassium iodide solution. If the instru-
follows: Connect the bottle to the Bendix apparatus and titrate
ment has been idle for some time, it is necessary to remove the
20 mL of the standardized KIO -KI solution with the thiosul-
ferric iron by running a disk of tinplate through the regular
fate solution using the same procedure as is used for making
procedure before test samples are run.
weight of coating determinations, but ignore the stripping unit.
The tin equivalent of the Na S O solution in pounds per base
2 2 3
6. Reagents
box is equal to: 20/A× T× 17.28, where A = millilitres of
sodium thiosulfate solution used in titrating 20 mL of standard
6.1 Purity of Reagents—Reagent grade chemicals shall be
KIO -KI solution. A chart can be prepared showing lb/bb/mL
used in all tests. Unless otherwise indicated, it is intended that
of thiosulfate.
all reagents shall conform to the specifications of the Commit-
tee on Analytical Reagents of the American Chemical Society 6.6 Sodium Thiosulfate, Standard Solution (for coatings
where such specifications are available. Other grades may be
0.50 lb/bb and under)—Dissolve 6.57 g of Na S O ·5 H O and
2 2 3 2
used, provided it is first ascertained that the reagent is of 2.78 g of NaOH in 1 litre of distilled water in a light-proof
sufficiently high purity to permit its use without lessening the
bottle. Larger quantities in the same proportions may be
accuracy of the determination. prepared if desired.Allow that solution to age for 72 h, remix,
and standardize by the same procedure used for the stronger
6.2 Water—Deionized or distilled water having a volume
Na S O solution but use only 10 mL of potassium iodate-
2 2 3
resistivity greater than 1 MΩ·cm at 25°C as determined by
potassium iodide solution.
Nonreferee Method of Test Methods D1125.
6.7 Starch Solution—Heat 200 mL of distilled water to
boiling in a Florence flask and slowly add 2.5 g of soluble
starch paste while the solution is agitated. Add the hot starch
Complete details and drawings of the apparatus are contained in U. S. Patent
solution to 500 mL of distilled water containing 2.5 g of
No. 2,455,726 entitled “Method for Electrolytic Stripping and Determination of
Plating Metals.”Asuitable commercial supplier of the apparatus has been found to
NaOH. Dilute to 1 L and thoroughly mix.
be the Wilkens-Anderson Company of Chicago.
Reagent Chemicals, American Chemical Society Specifications, American
7. Test Sample
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
7.1 Tin plate samples for coating weight determinations are
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
obtained by stamping disks 2.257 6 0.001 in. (57.33 6 0.02
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
2 2
MD. mm) in diameter which is equivalent to 4 in. (25.81 cm)of
A630 − 03 (2009)
2 2
area (8 in. (52 cm ) of surface area). Recommended methods METHOD B—DETERMINATION OF THE TIN
of obtaining representative samples are described in the Tin COATING WEIGHTS BY THE CONSTANT
Mill Products sections of the American Iron and Steel Insti- CURRENT, ELECTROLYTIC METHOD (REFEREE
tute’s Steel Products Manual. METHOD)
10. Scope
8. Procedure
10.1 This test method may be used to determine not only
8.1 Make required electrical connections.
thetotaltincoatingweightbutalsotodeterminethatpartofthe
8.2 Add HCl (1+1) to the porous tubes containing the
tin coating which is present as free tin and that part which is
carbon cathodes.
present in the alloyed form.
8.3 Suspend the sample disk of tin plate from the magnetic
11. Summary of Test Method
holder.
11.1 In this test method, the tin is stripped from a sample of
NOTE1—Ifitisdesiredtostripononesideonly,masktheoppositeside
tin-plate anodically at constant current in an electrolyte of the
and reduce the current to half its normal value. If a heavy oxide film has
hydrochloric acid. The potential difference developed between
developed on the tin plate during storage, the plate must be cathodically
the sample and a reference electrode is plotted against time on
cleaned prior to testing.
a strip chart recorder or an electric digital readout. The time
8.4 Place a measured quantity of standardized KIO -KI
required for stripping the free tin and alloyed tin, respectively,
solution into a 400-mL beaker (see 8.10). Simultaneously add
are read from the resulting chart (see Fig. 1) or a digital
250 mL of dilute HCl and mix thoroughly.
readout.Sincethestrippingcurrenthasbeenpreset,thefree-tin
and alloy-tin coating weights are calculated by employing
8.5 Raise the beaker so that the sample and porous cells are
Faraday’s law of electrolysis.
immersed.
8.6 Turn on d-c current and adjust to give 0.5 A/in. of
12. Calibration and Standardization
sample.
12.1 Determine the weight loss of pure tin specimens
8.7 Time for complete removal of tin (see 8.10).
electrolyzed for a given time interval, expressing the results as
milligrams or pounds of tin per base box per second.
8.8 Remove the beaker and add approximately 5 mL of
12.2 The test specimen should be a 4-in. disk of pure tin
starch indicator solution.
approximately 0.20 in. (5.1 mm) thick.
8.9 Titrate with standardized Na S O solution to the dis-
2 2 3
12.3 The milliammeter should be frequently checked using
appearance of the blue color.
a precision milliammeter.
8.10 The stripping times and amounts of KIO -KI solution
to use are as follows:
13. Available Constant Current Procedures
Amount of
13.1 There are two commercially available constant current,
Stripping KIO -KI
electrolytic units that are in common use. Either of the
Product Time, s Solution, mL
Electrolytic 100 90 20
following, or equivalent equipment, can be used as an accept-
Electrolytic 75 75 20
able referee method:
Electrolytic 50 60 10
13.1.1 Willey & Kunze Coulometric Test Method—Supplier
Electrolytic 25 60 10
Electrolytic 10 45 10 will provide set up, start up and running procedures.
13.1.2 The Stannomatic Test Method—Supplier will provide
Stripping time should not be longer than is required to
set up, start up and running procedures.
remove all of the tin. Results will be high by approximately
0.01 lb/bb for each minute of over-stripping.
14. Willey & Kunze Coulometric Test Method
14.1 In this test method, the tin is electrolytically removed
9. Reproducibility of Results
2 2
from a 4 in. (25.807 cm ) circular sample of tinplate anodi-
9.1 Arbitrary maximum spreads in intermill check tests
cally at constant current in an electrolyte of 1.0 N hydrochloric
show the reproducibility of test results by the Bendix Method
tobeasfollows: 60.02lb/bbfor0.25–lbcoatings, 60.03lb/bb
See Kunze, C. T., and Willey, A. R., “Electrolytic Determination of Tin and
for0.75-lbcoatings,and 60.04lb/bbfor1.25-lbcoatings.Data
Tin-Iron Alloy Coating Weights on Tin Plate,” Journal, Electrochemical Society,
have not been developed for 0.10-lb coatings.
Vol 99, No. 9, September 1952, pp. 354–359; and “Methods for Determination of
Coating Weights of Tin Plate,” American Iron and Steel Institute, December 1959,
pp. 19–26.
Available from Coulometric Systems, Bergholtz, OH.
5 8
Available from American Iron and Steel Institute (AISI), 1140 Connecticut Available from Products Distribution Service Division, WilkensAnderson Co.,
Ave., NW, Suite 705, Washington, DC 20036, http://www.steel.org. 4525 West Division St., Chicago, IL 60651.
A630 − 03 (2009)
FIG. 1 Representative Electrostripper Curve
acid. The potential difference developed between the sample 14.5 Sample Size:
and a glass calomel reference electrode is plotted against time
14.5.1 Tinplate samples for coating weight determinations
on a strip chart recorder. The time required for stripping the
are obtained by stamping discs 2.257 6 0.001 in. (57.33 6
2 2
free tin and alloy tin, respectively are read from the resulting
0.02 mm) in diameter. This is equivalent to 4 in. (25.81 cm )
chart (see Fig. 1) or on an electronic digital
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:A 630–98 Designation:A 630–03 (Reapproved 2009)
Standard Test Methods for
Determination of Tin Coating Weights for Electrolytic Tin
Plate
This standard is issued under the fixed designation A 630; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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.
INTRODUCTION
Fourtestmethodsfordeterminationoftincoatingweightsaredescribed.Thesearetypicalmethods
and represent those most commonly used in the tin plate industry. Publication of these test methods
is not intended to preclude the use of any other methods such as X-ray fluorescence measurement
systems for control purposes by the consumer or supplier. However, in case of dispute, the referee
method is to be used to determine conformance to Specification A624/A624M and Specification
A626/A626M.
Sampling procedures for tin coating-weight testing and applicable standards for the specific class
designation are outlined in Specification A624/A624M and Specification A626/A626M.
1. Scope
1.1 These test methods include four methods for the determination of tin coating weights for electrolytic tin plate as follows:
Test Method Sections
A—Bendix Test Method 3to9
B—Constant-Current, Electrolytic Test Method (Referee Method) 10 to 18
C—Sellar’s Test Method 19 to 28
D—Titration Test Method 29 to 37
1.2The values stated in inch-pound units are to be regarded as the standard.The values given in parentheses are for information
only.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions 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 responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
A599/A599M Specification for Tin Mill Products, Electrolytic Tin-Coated, Cold-Rolled Sheet
A623 Specification for Tin Mill Products, General Requirements
A623M Specification for Tin Mill Products, General Requirements (Metric) [Metric]
A624/A624M Specification for Tin Mill Products, Electrolytic Tin Plate, Single Reduced
A626/A626M Specification for Tin Mill Products, Electrolytic Tin Plate, Double Reduced
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
These test methods are under the jurisdiction of ASTM Committee A-1A01 on Steel, Stainless Steel and Related Alloys,Alloys and are the direct responsibility of
Subcommittee A01.20 on Tin Plate.
Current edition approved March 10, 1998. Published November 1998. Originally published asA630–68. Last previous editionA630–91 (Reapproved 1997). on Tin Mill
Products.
Current edition approved April 1, 2009. Published April 2009. Originally approved in 1968. Last previous edition approved in 2003 as A630-03.
Annual Book of ASTM Standards, Vol 01.06.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 630–03 (2009)
METHOD A—DETERMINATION OF THE TIN COATING WEIGHTS BY THE BENDIX TEST METHOD
3. Scope
3.1 This test method covers the determination of tin coating weights on steel plate.
4. Summary of Test Method
4.1 Theprocedureinvolvesdissolutionoftinfromatinplateanodeinadilutehydrochloricacidsolutioncontainingameasured
excess of standard potassium iodate-potassium iodide solution. Excess iodine from the iodate-iodide solution is back titrated with
standard sodium thiosulfate using a starch indicator.
5. Apparatus
5.1 The detinning cell consists essentially of two cathodes of carbon rod, the sample that serves as an anode, and a beaker of
dilute hydrochloric acid electrolyte.The carbon rods (6 by 0.25 in. or 152 by 6.35 mm, encased in porous porcelain thimbles) are
suspended from a suitable frame about 1 in. (25 mm) apart. A small glass-enclosed magnet is attached to the frame in such a
manner that it will hold the sample suspended midway between the two cathodes. A movable platform permits the beaker of
electrolyte to be brought up around the 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, a
motor-driven stirrer for titrations, and a timing switch when large numbers of determinations are to be made.
5.4 Precautions—Theapparatusmustbekeptincontinuousoperationtopreventironinthesolutionadheringtotheporouscells
fromoxidizingandsubsequentlyliberatingiodinefromthepotassiumiodate-potassiumiodidesolution.Iftheinstrumenthasbeen
idle for some time, it is necessary to remove the ferric iron by running a disk of tinplate through the regular procedure before test
samples are run.
6. Reagents
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
6.2 Water—Deionizedordistilledwaterhavingavolumeresistivitygreaterthan1MV·cmat25°CasdeterminedbyNonreferee
Method of Test Methods D1125.
6.3 Hydrochloric Acid (1.7to2.0 N)—Add1partofconcentratedhydrochloricacid(HCl,spgr1.19,36.5to38.0%)to5parts
of water and mix well.
6.4 Potassium Iodate-Potassium Iodide, Standard Solution (0.0975 N)—Dissolve 3.48 g of KIO , 21.74 g of KI, and 1.21 g of
NaOH in 1 L of distilled water. Standardize as follows: Transfer 0.2700 g of National Bureau of Standards tin to a 500-mL
Erlenmeyer flask.Add 200 mLof HCl (1+1). Connect the flask to a carbon dioxide (CO ) system and displace the air in the flask
with CO . While continuing the flow of CO , heat the flask but do not boil violently. After the tin has dissolved add 0.5 g of
2 2
antimony and2gof high-purity aluminum. 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 CO . Disconnect from the CO system
2 2
and titrate with the KIO -KI solution using starch as an indicator. Calculate the tin titer, T, as follows:
T 5 A/B
where:
A = tin used (0.2700 g),
B = KIO -KI solution used for titration, mL, and
T = tin titer for above KIO -KI solution, (grams of tin/mL),
2 2
T = 17.28 = lb/base box (bb)/mL, for a 4-in. (25.81-cm ) sample.
6.5 Sodium Thiosulfate, Standard Solution (for coatings over 0.50 lb/bb)—Dissolve 15.11 g of Na S O ·5 H O and 1.11 g of
2 2 3 2
NaOH 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 KIO -KI solution with the thiosulfate solution
using the same procedure as is used for making weight of coating determinations, but ignore the stripping unit.The tin equivalent
Annual Book of ASTM Standards, Vol 11.01.
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 Plating
Metals.” A suitable commercial supplier of the apparatus has been found to be the Wilkens-Anderson Company of Chicago.
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 Plating
Metals.” A suitable commercial supplier of the apparatus has been found to be the Wilkens-Anderson Company of Chicago.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
A 630–03 (2009)
oftheNa S O solutioninpoundsperbaseboxisequalto:20/A 3 T 317.28,where A=millilitresofsodiumthiosulfatesolution
2 2 3
used in titrating 20 mL of standard KIO -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 Na S O ·5 H O and 2.78
2 2 3 2
gofNaOHin1litreofdistilledwaterinalight-proofbottle.Largerquantitiesinthesameproportionsmaybepreparedifdesired.
Allow that solution to age for 72 h, remix, and standardize by the same procedure used for the stronger Na S O solution but use
2 2 3
only 10 mL of potassium iodate-potassium iodide solution.
6.7 Starch Solution—Heat 200 mLof distilled water to boiling in a Florence flask and slowly add 2.5 g of soluble starch paste
while the solution is agitated. Add the hot starch solution to 500 mL of distilled water containing 2.5 g of NaOH. Dilute to 1 L
and thoroughly mix.
7. Test Sample
7.1 Tin plate samples for coating weight determinations are obtained by stamping disks 2.257 6 0.001 in. (57.33 6 0.02 mm)
2 2 2 2
in diameter which is equivalent to 4 in. (25.81 cm ) of area (8 in. (52 cm ) of surface area). Recommended methods of obtaining
representative samples are described in the Tin Mill Products sections of the American Iron and Steel Institute’s Steel Products
Manual.
8. Procedure
8.1 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 1—If it is desired to strip on one side only, mask the opposite side and reduce the current to half its normal value. If a heavy oxide film has
developed on the tin plate during storage, the plate must be cathodically cleaned prior to testing.
8.4 Place a measured quantity of standardized KIO -KI solution into a 400-mLbeaker (see 8.10). Simultaneously add 250 mL
of 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. 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 solution.
8.9 Titrate with standardized Na S O solution to the disappearance of the blue color.
2 2 3
8.10 The stripping times and amounts of KIO -KI solution to use are as follows:
Amount of
Stripping KIO -KI
Product Time, s Solution, mL
Electrolytic 100 90 20
Electrolytic 75 75 20
Electrolytic 50 60 10
Electrolytic 25 60 10
Electrolytic 10 45 10
Stripping time should not be longer than is required to remove all of the tin. Results will be high by approximately 0.01 lb/bb
for each minute of over-stripping.
9. Reproducibility of Results
9.1 Arbitrary maximum spreads in intermill check tests show the reproducibility of test results by the Bendix Method to be as
follows: 60.02 lb/bb for 0.25–lb coatings, 60.03 lb/bb for 0.75-lb coatings, and 60.04 lb/bb for 1.25-lb coatings. Data have not
been developed for 0.10-lb coatings.
METHOD B—DETERMINATION OF THE TIN COATING WEIGHTS BY THE CONSTANT CURRENT,
ELECTROLYTIC METHOD (REFEREE METHOD)
10. Scope
10.1 This test method may be used to determine not only the total tin coating weight but also to determine that part of the tin
coating which is present as free tin and that part which is present in the alloyed form.
Reagent Chemicals,American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
Available from American Iron and Steel Institute (AISI), 1140 Connecticut Ave., NW, Suite 705, Washington, DC 20036, http://www.steel.org.
Available from the American Iron and Steel Institute, 150 E. 42nd St., New York, NY.
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. 354–359; and “Methods for Determination of Coating Weights of Tin Plate,” American Iron and Steel Institute, December 1959, pp. 19–26.
A 630–03 (2009)
11. Summary of Test Method
11.1 In this test method, the tin is stripped from a sample of tin-plate anodically at constant current in an electrolyte of the
hydrochloric acid. The potential difference developed between the sample and a reference electrode is plotted against time on a
strip chart recorder or an electric digital readout.The time required for stripping the free tin and alloyed tin, respectively, are read
from the resulting chart (see Fig. 1) or a digital readout. Since the stripping current has been preset, the free-tin and alloy-tin
coating weights are calculated by employing Faraday’s law of electrolysis.
12. Calibration and Standardization
12.1 Determinetheweightlossofpuretinspecimenselectrolyzedforagiventimeinterval,expressingtheresultsasmilligrams
or pounds of tin per base box per second.
12.2 The test specimen should be a 4-in. 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 Procedures
13.1 There are two commercially available constant current, electrolytic units that are in common use. Either of the following,
or equivalent
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