ASTM B866-95(2018)

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.
Designation: B866 −95 (Reapproved 2018)
Standard Test Method for
Gross Defects and Mechanical Damage in Metallic Coatings
by Polysulfide Immersion
This standard is issued under the fixed designation B866; 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.
1. Scope 2. Referenced Documents
1.1 This test method covers equipment and methods for 2.1 ASTM Standards:
detecting gross defects and mechanical damage (including B246Specification for Tinned Hard-Drawn and Medium-
wear-through) in metallic coatings where the breaks in the Hard-Drawn Copper Wire for Electrical Purposes
coating penetrate down to a copper or copper alloy substrate. B374Terminology Relating to Electroplating
B488Specification for Electrodeposited Coatings of Gold
1.2 This test method is suitable for coatings consisting of
for Engineering Uses
single or combined layers of any coating that does not
B542Terminology Relating to Electrical Contacts andTheir
significantly tarnish in an alkaline polysulfide solution. Ex-
Use
amples are gold, nickel, tin, tin-lead, and palladium, or their
B545Specification for Electrodeposited Coatings of Tin
alloys.
B605Specification for Electrodeposited Coatings of Tin-
1.3 Recent reviews of porosity testing (which include those
Nickel Alloy
for gross defects) and testing methods can be found in
B679Specification for Electrodeposited Coatings of Palla-
2,3
literature. An ASTM guide to the selection of porosity and
dium for Engineering Use
gross defect tests for electrodeposits and related metallic
B689Specification for Electroplated Engineering Nickel
coatingsisavailableasGuideB765.Otherrelatedporositytest
Coatings
standards are Test Methods B735, B741, B798, B799, and
B733Specification for Autocatalytic (Electroless) Nickel-
B809.
Phosphorus Coatings on Metal
1.4 The values stated in SI units are to be regarded as the B735Test Method for Porosity in Gold Coatings on Metal
Substrates by Nitric Acid Vapor
standard. The values given in parentheses are for information
B741Test Method for Porosity In Gold Coatings On Metal
only.
Substrates By Paper Electrography (Withdrawn 2005)
1.5 This standard does not purport to address all of the
B765GuideforSelectionofPorosityandGrossDefectTests
safety concerns, if any, associated with its use. It is the
for Electrodeposits and Related Metallic Coatings
responsibility of the user of this standard to establish appro-
B798Test Method for Porosity in Gold or Palladium Coat-
priate safety, health, and environmental practices and deter-
ings on Metal Substrates by Gel-Bulk Electrography
mine the applicability of regulatory limitations prior to use.
B799Test Method for Porosity in Gold and Palladium
1.6 This international standard was developed in accor-
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
dance with internationally recognized principles on standard-
B809Test Method for Porosity in Metallic Coatings by
ization established in the Decision on Principles for the
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3. Terminology
Barriers to Trade (TBT) Committee.
3.1 Definitions: Many terms used in this test method are
defined in Terminologies B374 or B542.
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
3.2 Definitions of Terms Specific to This Standard:
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
Test Methods.
Current edition approved Aug. 1, 2018. Published August 2018. Originally
approvedin1995.Lastpreviouseditionapprovedin2013asB866–95(2013).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/B0866-95R18. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Clarke, M., “Porosity and Porosity Tests,” in Properties of Electrodeposits, Standards volume information, refer to the standard’s Document Summary page on
edited by Sard, Leidheiser, and Ogburn,The Electrochemical Society, 1975, p. 122. the ASTM website.
3 5
Krumbein, S. J., “PorosityTesting of Contact Platings,”Trans. Connectors and The last approved version of this historical standard is referenced on
Interconnection Technology Symposium, Philadelphia, PA, October 1987, p. 47. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B866 − 95 (2018)
3.2.1 defect indications—black or dark colored products 5.2 Theprotectionaffordedbywellappliedcoatingsmaybe
resulting from the reaction between the alkaline polysulfide diminished by improper handling following plating or as a
reagent and exposed copper or copper alloy underlying metal. resultofwearormechanicaldamageduringtestingorwhilein
service. The alkaline polysulfide test serves to indicate if the
3.2.2 gross defects—breaks in the coating that expose rela-
damage has extended down to the copper or copper alloy basis
tively large areas of underlying metal to the environment
metal since it will not detect exposed nickel underplate.
(comparewith intrinsic porosity(3.2.3)).Grossdefectsinclude
thoseproducedbymechanicaldamageandwear,inadditionto
5.3 The alkaline polysulfide test has been specified in
as-plated large pores (with diameters an order of magnitude
several ASTM specifications for tin-plated coatings, namely
greater than intrinsic porosity) and networks of microcracks.
Specifications B246 and B545. This test could also be used to
detect gross defects and mechanical damage in other metallic
NOTE 1—Such large pores and microcrack networks indicate serious
coatings, such as tin-nickel alloy (Specification B605), nickel
deviations from acceptable coating practice (as, for example, dirty
basis-metal substrates and contaminated or out-of-balance plating baths). (Specification B689), gold (Specification B488), palladium
(Specification B679), and autocatalytic nickel-phosphorous
3.2.3 intrinsic porosity—the “normal” porosity that is
coatings (Specification B733).
present, to some degree, in all commercial thin platings (such
as in precious-metal coatings for engineering purposes) and
5.4 This test detects mechanical damage that exposes cop-
will generally follow an inverse relationship with thickness.
perunderplateandcopperbasismetal.Suchdamagemayoccur
in any post-plating operation or even towards the end of the
NOTE 2—Intrinsic porosity is due primarily to small deviations from
ideal plating and surface preparation conditions. Scanning electron mi- plating operation. It is most often seen to occur in product
croscope(SEM)studieshaveshownthatthediameterofsuchpores,atthe
assembly operations.
plating surface, is of the order of micrometres, so that only small areas of
5.5 If properly performed, this test will also detect wear-
underlying metal are exposed to the environment.
through, provided the wear-through reaches a copper or
3.2.4 measurement area—the portion or portions of the
copper-alloy layer.
surfaceexaminedforthepresenceofgrossdefectsormechani-
caldamage(andwear-through).Themeasurementareashallbe
5.6 Many types of gross defects are too small to be seen,
indicated on the drawings of the parts, or by the provision of
except at magnifications so high (as in SEM) that a realistic
suitably marked samples.
assessment of the measurement area cannot be easily made.
Other defects, such as many types of wear-through, provide
3.2.5 metallic coatings—platings, claddings, or other metal-
insufficient contrast with the coating surface. Gross defects
lic coatings applied to the basis-metal substrate. The coating
tests(aswithporositytests)are,therefore,usedtomagnifythe
can comprise a single metallic layer or a combination of
defect sites by producing visible reaction products in and
metallic layers.
around the defects.
3.2.6 porosity (general)—in a coating, the presence of any
hole,crack,orotherdefectthatexposestheunderlyingmetalto 5.7 The polysulfide solution will react with copper and
copperalloystoproduceadarkbrownorblackstain(thedefect
the environment.
indications) at the site of the defect. Silver also turns black
3.2.7 underplate—ametalliccoatinglayerbetweenthebasis
underthesameconditions.Thetestsolutionwillnotreactwith
metal and the topmost metallic coating. The thickness of an
nickel and is only useful when the presence or absence of
underplatingisusuallygreaterthan1µm,incontrasttoastrike
copper exposure is a specific requirement.
or flash, which is usually thinner.
5.8 The polysulfide immersion test is relatively insensitive
3.2.8 wear-through—the exposure of underplate or basis
to the presence of small pores. It shall not be used as a general
metal as a direct result of wear. Wear-through is an observable
porosity test. (Test Method B809 should be used instead.)
phenomenon.
3.2.9 wear track—a mark that indicates the path along 5.9 Theextentandlocationofthegrossdefectsormechani-
cal damage (revealed by this test) may or may not be
whichphysicalcontacthadbeenmadeduringaslidingprocess
(such as the mating and unmating of an electrical contact). detrimental to product performance or service life. Such
determinations shall be made by the user of the test through
4. Summary of Test Method
practical experience or judgment.
4.1 Thetestsamplesareimmersedinanalkalinepolysulfide
5.10 The present test can be used on samples of various
solution at 74°C (165°F) for 60 s.After rinsing and drying, the
geometries, such as curved surfaces. It can also be used for
samples are examined for dark or discolored areas which
selectiveareacoatingifallowanceismadefortarnishcreepage
indicate exposure of copper or copper alloys to the solution
from bare copper alloy areas.
through breaks in the coating.
5.11 Thistestisdestructiveinthatitrevealsthepresenceof
gross defects by contaminating the surface with reaction-
5. Significance and Use
productfilms.Anypartsexposedtothistestshallnotbeplaced
5.1 Thepurposeofthealkalinepolysulfideimmersiontestis
in service.
to determine the presence of mechanical damage, wear-
through, and other gross defects in the coating. Most metallic 5.12 However,thedefectindicationsonthesamplesurfaces
coatingsareintendedtobeprotectiveandthepresenceofgross thatresultfromthistestarestable;samplesmayberetainedfor
defects indicates a serious reduction of such protection. reference purposes.
B866 − 95 (2018)
5.13 This test is neither recommended for predictions of usingahydrometerto1.142 60.005,at20to30°C,byadding
p
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