ASTM B866-95(2003)
(Test Method)Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
SCOPE
1.1 This test method covers equipment and methods for detecting gross defects and mechanical damage (including wear-through) in metallic coatings where the breaks in the coating penetrate down to a copper or copper alloy substrate.
1.2 This test method is suitable for coatings consisting of single or combined layers of any coating that does not significantly tarnish in an alkaline polysulfide solution. Examples are gold, nickel, tin, tin-lead, and palladium, or their alloys.
1.3 Recent reviews of porosity testing (which include those for gross defects) and testing methods can be found in literature. An ASTM guide to the selection of porosity and gross defect tests for electrodeposits and related metallic coatings is available as Guide B 765. Other related porosity test standards are Test Methods B 735, B 741, B 798, B 799, and B 809.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 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.
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Designation: B 866 – 95 (Reapproved 2003)
Standard Test Method for
Gross Defects and Mechanical Damage in Metallic Coatings
by Polysulfide Immersion
This standard is issued under the fixed designation B 866; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope for Engineering Uses
B 542 Terminology Relating to Electrical Contacts and
1.1 This test method covers equipment and methods for
Their Use
detecting gross defects and mechanical damage (including
B 545 Specification for Electrodeposited Coatings of Tin
wear-through) in metallic coatings where the breaks in the
B 605 Specification for Electrodeposited Coatings of Tin-
coating penetrate down to a copper or copper alloy substrate.
Nickel Alloy
1.2 This test method is suitable for coatings consisting of
B 679 Specification for Electrodeposited Coatings of Palla-
single or combined layers of any coating that does not
dium for Engineering Use
significantly tarnish in an alkaline polysulfide solution. Ex-
B 689 Specification for Electrodeposited Engineering
amples are gold, nickel, tin, tin-lead, and palladium, or their
Nickel Coatings
alloys.
B 733 Specification for Autocatalytic (Electroless) Nickel-
1.3 Recent reviews of porosity testing (which include those
Phosphorus Coatings on Metal
for gross defects) and testing methods can be found in
,
2 3
B 735 Test Method for Porosity in Gold Coatings on Metal
literature. An ASTM guide to the selection of porosity and
Substrates by Nitric Acid Vapor
gross defect tests for electrodeposits and related metallic
B 741 Test Method for Porosity in Gold Coatings on Metal
coatingsisavailableasGuideB 765.Otherrelatedporositytest
Substrates by Paper Electrography
standards are Test Methods B 735, B 741, B 798, B 799, and
B 765 Guide for Selection of Porosity Tests for Electrode-
B 809.
posits and Related Metallic Coatings
1.4 The values stated in SI units are to be regarded as the
B 798 Test Method for Porosity in Gold or Palladium
standard. The values given in parentheses are for information
Coatings on Metal Substrates by Gel-Bulk Electrography
only.
B 799 Test Method for Porosity in Gold and Palladium
1.5 This standard does not purport to address all of the
Coatings by Sulfurous Acid/Sulfur Dioxide Vapor
safety concerns, if any, associated with its use. It is the
B 809 Test Method for Porosity in Metallic Coatings by
responsibility of the user of this standard to establish appro-
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3. Terminology
2. Referenced Documents 3.1 Definitions: Many terms used in this test method are
defined in Terminologies B 374 or B 542.
2.1 ASTM Standards:
3.2 Definitions of Terms Specific to This Standard:
B 246 Specification for Tinned Hard-Drawn and Medium-
4 3.2.1 defect indications—black or dark colored products
Hard-Drawn Copper Wire for Electrical Purposes
resulting from the reaction between the alkaline polysulfide
B 374 Terminology Relating to Electroplating
reagent and exposed copper or copper alloy underlying metal.
B 488 Specification for Electrodeposited Coatings of Gold
3.2.2 gross defects—breaks in the coating that expose rela-
tively large areas of underlying metal to the environment
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
(compare with intrinsic porosity (3.2.3)). Gross defects include
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
those produced by mechanical damage and wear, in addition to
Test Methods.
as-plated large pores (with diameters an order of magnitude
Current edition approved Feb. 10, 2003. Published May 2003. Originally
approved in 1995. Last previous edition approved in 1995 as B 866 – 95. greater than intrinsic porosity) and networks of microcracks.
Clarke, M., “Porosity and Porosity Tests,” in Properties of Electrodeposits,
NOTE 1—Such large pores and microcrack networks indicate serious
edited by Sard, Leidheiser, and Ogburn, The Electrochemical Society, 1975, p. 122.
deviations from acceptable coating practice (as, for example, dirty
Krumbein, S. J., “Porosity Testing of Contact Platings,” Trans. Connectors and
Interconnection Technology Symposium, Philadelphia, PA, October 1987, p. 47.
Annual Book of ASTM Standards, Vol 02.03.
5 6
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 02.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 866 – 95 (2003)
basis-metal substrates and contaminated or out-of-balance plating baths).
(Specification B 679), and autocatalytic nickel-phosphorous
coatings (Specification B 733).
3.2.3 intrinsic porosity—the “normal” porosity that is
5.4 This test detects mechanical damage that exposes cop-
present, to some degree, in all commercial thin platings (such
perunderplateandcopperbasismetal.Suchdamagemayoccur
as in precious-metal coatings for engineering purposes) and
in any post-plating operation or even towards the end of the
will generally follow an inverse relationship with thickness.
plating operation. It is most often seen to occur in product
NOTE 2—Intrinsic porosity is due primarily to small deviations from
assembly operations.
ideal plating and surface preparation conditions. Scanning electron mi-
5.5 If properly performed, this test will also detect wear-
croscope (SEM) studies have shown that the diameter of such pores, at the
through, provided the wear-through reaches a copper or
plating surface, is of the order of micrometres, so that only small areas of
underlying metal are exposed to the environment. copper-alloy layer.
5.6 Many types of gross defects are too small to be seen,
3.2.4 measurement area—the portion or portions of the
except at magnifications so high (as in SEM) that a realistic
surface examined for the presence of gross defects or mechani-
assessment of the measurement area cannot be easily made.
caldamage(andwear-through).Themeasurementareashallbe
Other defects, such as many types of wear-through, provide
indicated on the drawings of the parts, or by the provision of
insufficient contrast with the coating surface. Gross defects
suitably marked samples.
tests (as with porosity tests) are, therefore, used to magnify the
3.2.5 metallic coatings—platings, claddings, or other metal-
defect sites by producing visible reaction products in and
lic coatings applied to the basis-metal substrate. The coating
around the defects.
can comprise a single metallic layer or a combination of
5.7 The polysulfide solution will react with copper and
metallic layers.
copperalloystoproduceadarkbrownorblackstain(thedefect
3.2.6 porosity (general)—in a coating, the presence of any
indications) at the site of the defect. Silver also turns black
hole,crack,orotherdefectthatexposestheunderlyingmetalto
under the same conditions.The test solution will not react with
the environment.
nickel and is only useful when the presence or absence of
3.2.7 underplate—a metallic coating layer between the
copper exposure is a specific requirement.
basis metal and the topmost metallic coating. The thickness of
5.8 The polysulfide immersion test is relatively insensitive
an underplating is usually greater than 1 µm, in contrast to a
to the presence of small pores. It shall not be used as a general
strike or flash, which is usually thinner.
porosity test. (Test Method B 809 should be used instead.)
3.2.8 wear-through—the exposure of underplate or basis
5.9 The extent and location of the gross defects or mechani-
metal as a direct result of wear. Wear-through is an observable
cal damage (revealed by this test) may or may not be
phenomenon.
detrimental to product performance or service life. Such
3.2.9 wear track—a mark that indicates the path along
determinations shall be made by the user of the test through
which physical contact had been made during a sliding process
practical experience or judgment.
(such as the mating and unmating of an electrical contact).
5.10 The present test can be used on samples of various
geometries, such as curved surfaces. It can also be used for
4. Summary of Test Method
selective area coating if allowance is made for tarnish creepage
4.1 Thetestsamplesareimmersedinanalkalinepolysulfide
from bare copper alloy areas.
solution at 74°C (165°F) for 60 s.After rinsing and drying, the
5.11 This test is destructive in that it reveals the presence of
samples are examined for dark or discolored areas which
gross defects by contaminating the surface with reaction-
indicate exposure of copper or copper alloys to the solution
product films.Any parts exposed to this test shall not be placed
through breaks in the coating.
in service.
5.12 However, the defect indications on the sample surfaces
5. Significance and Use
thatresultfromthistestarestable;samplesmayberetainedfor
5.1 Thepurposeofthealkalinepolysulfideimmersiontestis
reference purposes.
to determine the presence of mechanical damage, wear-
5.13 This test is neither recommended for predictions of
through, and other gross defects in the coating. Most metallic
product performance nor is it intended to simulate field failure
coatings are intended to be protective and the presence of gross
mechanisms. For such product performance evaluations, an
defects indicates a serious reduction of such protection.
environmental test that is known to simulate actual failure
5.2 The protection afforded by well applied coatings may be
mechanisms should be used.
diminished by improper handling following plating or as a
result of wear or mechanical damage during testing or while in
6. Apparatus
service. The alkaline polysulfide test serves to indicate if the
6.1 In addition to the normal equipment (beakers, bottles,
damage has extended down to the copper or copper alloy basis
metal since it will not detect exposed nickel underplate. weighing balances, funnels, and so forth) that are part of every
chemical laboratory, the following apparatus are required:
5.3 The alkaline polysulfide test has been specified in
several ASTM specifications for tin-plated coatings, namely 6.1.1 Microscope—Optical, stereo, 10 to 303. It is pre-
Specifications B 246 and B 545.This test could also be used to ferred that one eyepiece contain a graduated reticle for mea-
detect gross
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