ASTM D3718-85A(2022)e1

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D3718 − 85a (Reapproved 2022)
Standard Test Method for
Low Concentrations of Chromium in Paint by Atomic
Absorption Spectroscopy
This standard is issued under the fixed designation D3718; 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 U.S. Department of Defense.
ε NOTE—Footnote 4 was updated editorially in June 2022.
1. Scope tent of Paint and Related Coatings
1.1 This test method covers the determination of the content
3. Summary of Test Method
of chromium (including chromium oxide) in the range between
3.1 The sample of liquid coating or dried film is prepared
0.005 and 1.0 % present in the solids of liquid coatings or in
foranalysisbydryashingat500 °Cfollowedbydigestionwith
dried films obtained from previously coated substrates. There
potassium permanganate and sulfuric acid in a polytetrafluo-
is no reason to believe that higher levels could not be
roethylene (PTFE)-lined acid decomposition vessel at an
determined by this test method, provided that appropriate
elevated temperature. The chromium in the filtered digestion
dilutions and adjustments in specimen size and reagent quan-
mixture is determined by atomic absorption spectroscopy.
tities are made.
1.2 The values stated in SI units are to be regarded as
4. Significance and Use
standard. No other units of measurement are included in this
4.1 The permissible level of heavy metals in certain coat-
standard.
ingsisspecifiedbygovernmentalregulatoryagencies.Thistest
1.3 This standard does not purport to address all of the
methodprovidesafullydocumentedprocedurefordetermining
safety concerns, if any, associated with its use. It is the
low concentrations of chromium present in both water- and
responsibility of the user of this standard to establish appro-
solvent-reducible coatings to determine compliance.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Apparatus
Specific hazard statements are given in Section 7.
5.1 Atomic Absorption Spectrophotometer, consisting of an
1.4 This international standard was developed in accor-
atomizer and either a single- or three-slot burner; gas pressure-
dance with internationally recognized principles on standard-
regulating and metering devices for nitrous oxide (N O) and
ization established in the Decision on Principles for the
acetylene; a chromium hollow cathode lamp with a regulated
Development of International Standards, Guides and Recom-
constant current supply; a monochromator and associated
mendations issued by the World Trade Organization Technical
optics; a photosensitive detector connected to an electronic
Barriers to Trade (TBT) Committee.
amplifier; and a readout device.
2. Referenced Documents
5.2 Muffle Furnace, maintained at 500 6 10 °C.
2.1 ASTM Standards:
5.3 Force-Draft Oven, maintained at 105 6 2 °C.
D1193 Specification for Reagent Water 3
5.4 Acid Decomposition Vessel, with PTFE digestion cup.
D2832 GuideforDeterminingVolatileandNonvolatileCon-
5.5 Hot Plate, with variable surface temperature control
over the range from 70 to 200 °C.
This test method is under the jurisdiction of ASTM Committee D01 on Paint
5.6 Volumetric Flasks, 50, 100, and 1000-mL.
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.
CurrenteditionapprovedJune1,2022.PublishedJuly2022.Originallyapproved
in 1978. Last previous edition approved in 2015 as D3718 – 85a (2015). DOI: The sole source of supply of an acid decomposition cup, (Catalog Number
10.1520/D3718-85AR22E01. 4745), known to the committee at this time is the Parr Instrument Co., 211
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Fifty-third St., Moline, IL 61265. If you are aware of alternative suppliers, please
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM provide this information toASTM International Headquarters. Your comments will
Standards volume information, refer to the standard’s Document Summary page on receive careful consideration at a meeting of the responsible technical committee,
the ASTM website. which you may attend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D3718 − 85a (2022)
5.7 Pipets, 5, 10, 15, and 20-mL capacity. 7.2 The National Institute for Occupational Safety and
Health has stated that hexavalent chromium compounds are
5.8 Filter Paper, ashless, medium filtering 15-cm.
hazardous to health. Care should be exercised in preparation of
5.9 Paint Shaker.
a sample for test. The wearing of a respirator and rubber or
synthetic gloves is recommended. In case of contact, wash
5.10 Crucibles, wide form, porcelain, approximately 30-mL
capacity. thoroughly with soap and water. Mixtures containing hexava-
lent chromium compounds should not be flushed down a drain
5.11 Mortar and Pestle.
but disposed of as hazardous waste.
5.12 Paint Draw-Down Bar.
7.3 Use only a rubber bulb aspirator for pipetting liquids.
6. Reagents
8. Calibration and Standardization
6.1 Purity of Reagents—Reagent grade chemicals shall be
8.1 Prepare 50-mL quantities of at least four standard
used in all tests. Unless otherwise indicated, it is intended that
solutions bracketing the expected chromium concentration in
all reagents shall conform to the specifications of the Commit-
the sample to be tested. To suitable aliquots of the 100-ppm
tee onAnalytical Reagents of theAmerican Chemical Society,
chromium standard working solution, add 10 mL of the
where such specifications are available. Other grades may be
oxidizing solution with a pipet, followed by the dropwise
used, provided it is first ascertained that the reagent is of
addition of reducing solution until the permanganate color has
sufficiently high purity to permit its use without lessening the
been discharged, then dilute to 50 mL with water.
accuracy of the determination.
8.2 Operational instructions for atomic absorption spectro-
6.2 Purity of Water—Unless otherwise indicated, references
photometers vary with different models. Consult the manufac-
towatershallbeunderstoodtomeanreagentwaterconforming
turer’s literature for establishing optimum conditions for the
to Type II of Specification D1193.
specific instrument used.
6.3 Chromium Standard Stock Solution (1 mg/mL)—
8.3 Turn the instrument on and set the wavelength to the
Dissolve 3.735 g of potassium chromate (K CrO ) in 100 mL
2 4
357.9-nm chromium line. Apply the recommended current to
of water and dilute to 1 L.
the chromium hollow-cathode lamp. Allow the instrument to
warm up for about 15 min and set the slit width. Adjust the
6.4 Chromium Standard Working Solution (0.1 mg/mL)—
Pipet 10 mL of the chromium standard stock solution into a nitrous oxide and acetylene pressures and ignite the burner
according to instructions.
100-mL volumetric flask and dilute to volume with water.
8.4 Aspirate water to rinse the atomizer chamber.Aspirate a
6.5 Oxidizing Solution—Dissolve 0.2 g of potassium per-
standard solution and make any necessary readjustment in
manganate (KMnO ) in 100 mL of H SO (1 + 1). Stir until
4 2 4
instrumentparameterstoobtainmaximumabsorption.Zerothe
completely dissolved. The color of this solution is dark brown.
instrument while aspirating reagent blank solution (6.7).Aspi-
6.6 Reducing Solution—Dissolve1gof hydroxylamine
rate each of the appropriate standard solutions and record the
hydrochloride (NH OH·HCl) in 100 mL of water.
corresponding instrument readings. Aspirate water between
6.7 Reagent Blank—Pipet 5 mL of oxidizing solution into
each standard.
25 mL of water contained in a 50-mL volumetric flask. Add
8.5 Transfer a 25-mL aliquot from each of the standard
reducing solution dropwise until the permanganate color has
solutions prepared in 8.1 to 50-mLvolumetric flasks and dilute
been discharged; then dilute to 50 mL with water.
to volume with water. Repeat the steps outlined in 8.4 for the
6.8 Sulfuric Acid (1+1)—Carefully add 1 volume of con-
diluted aliquot solutions.
centrated H SO (sp gr 1.84) to 1 volume of water.
2 4
8.6 Construct a calibration curve on linear graph paper by
6.9 Sulfuric Acid (5 % volume per volume)—Carefully add
plotting the a
...