ASTM B877-96(2018)
(Test Method)Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by the Phosphomolybdic Acid (PMA) Method
Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by the Phosphomolybdic Acid (PMA) Method
SIGNIFICANCE AND USE
5.1 The primary purpose of the PMA test is to determine the presence of mechanical damage, wear through, and other gross defects in the coating. Most metallic coatings are intended to be protective, and the presence of gross defects indicates a serious reduction of such protection.
5.2 The protection afforded by well applied coatings may be diminished by improper handling following plating or as a result of wear or mechanical damage during testing or while in service. The PMA test can serve to indicate the existence of such damage.
5.3 This test is used to detect underplate and substrate metal exposed through normal wear during relative motions (mating of electrical contacts) or through mechanical damage. As such, it is a sensitive pass/fail test and, if properly performed, will rapidly detect wear through to base metals or scratches that enter the base metal layers.
5.4 This test is relatively insensitive to small pores. It is not designed to be a general porosity test and shall not be used as such. The detection of pores will depend upon their sizes and the length of time that the reagent remains a liquid.
5.5 This test cannot distinguish degrees of wear through or whether the wear through is to nickel or copper. Once base metal is exposed, the colored molybdenum complex is formed. While relatively small area defects (compared to the area of the droplet) may be seen at the bottom of the drop as tiny colored regions immediately after applying the PMA, any larger areas of exposed base metal will cause the entire droplet to turn dark instantly.
5.6 The PMA test also detects mechanical damage that exposes underplate and substrate metal. Such damage may occur in any postplating operation or even at the end of the plating operation. It can often occur in assembly operations where plated parts are assembled into larger units by mechanical equipment.
5.7 The PMA test identifies the locations of exposed base metal. The extent and location of these exposed...
SCOPE
1.1 This test standard covers equipment and methods for using phosphomolybdic acid (PMA) to detect gross defects and mechanical damage including wear through in metallic coatings of gold, silver, or palladium. These metals comprise the topmost metallic layers over substrates of nickel, copper, or copper alloys.
1.2 Recent reviews of porosity testing, which include those for gross defects, and testing methods can be found in the literature.2, 3 An ASTM guide to the selection of porosity and gross defect tests for electrodeposits and related metallic coatings is available as Guide B765. Other related porosity and gross defects test standards are Test Methods B735, B741, B798, B799, B809, and B866, Specifications B488, B679,and B689.
1.3 The values stated in SI units are the preferred units. Those in parentheses are for information only.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
General Information
Relations
Standards Content (Sample)
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: B877 − 96 (Reapproved 2018)
Standard Test Method for
Gross Defects and Mechanical Damage in Metallic Coatings
by the Phosphomolybdic Acid (PMA) Method
This standard is issued under the fixed designation B877; 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 standard covers equipment and methods for
2.1 ASTM Standards:
usingphosphomolybdicacid(PMA)todetectgrossdefectsand
B374Terminology Relating to Electroplating
mechanical damage including wear through in metallic coat-
B488Specification for Electrodeposited Coatings of Gold
ings of gold, silver, or palladium. These metals comprise the
for Engineering Uses
topmost metallic layers over substrates of nickel, copper, or
B542Terminology Relating to Electrical Contacts andTheir
copper alloys.
Use
1.2 Recent reviews of porosity testing, which include those
B679Specification for Electrodeposited Coatings of Palla-
for gross defects, and testing methods can be found in the
dium for Engineering Use
2,3
literature. An ASTM guide to the selection of porosity and
B689Specification for Electroplated Engineering Nickel
gross defect tests for electrodeposits and related metallic
Coatings
coatingsisavailableasGuideB765.Otherrelatedporosityand
B735Test Method for Porosity in Gold Coatings on Metal
gross defects test standards are Test Methods B735, B741,
Substrates by Nitric Acid Vapor
B798, B799, B809, and B866, Specifications B488, B679,and
B741Test Method for Porosity In Gold Coatings On Metal
B689. 5
Substrates By Paper Electrography (Withdrawn 2005)
1.3 The values stated in SI units are the preferred units. B765GuideforSelectionofPorosityandGrossDefectTests
Those in parentheses are for information only.
for Electrodeposits and Related Metallic Coatings
B798Test Method for Porosity in Gold or Palladium Coat-
1.4 This standard does not purport to address all of the
ings on Metal Substrates by Gel-Bulk Electrography
safety concerns, if any, associated with its use. It is the
B799Test Method for Porosity in Gold and Palladium
responsibility of the user of this standard to establish appro-
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. B809Test Method for Porosity in Metallic Coatings by
1.5 This international standard was developed in accor- Humid Sulfur Vapor (“Flowers-of-Sulfur”)
dance with internationally recognized principles on standard- B866Test Method for Gross Defects and Mechanical Dam-
ization established in the Decision on Principles for the
age in Metallic Coatings by Polysulfide Immersion
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 in this test method are defined
in Terminology B374 or B542
1 3.2 Definitions of Terms Specific to This Standard:
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
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
approvedin1996.Lastpreviouseditionapprovedin2013asB877–96(2013).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/B0877-96R18. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Clarke,M.,“PorosityandPorosityTests,” Properties of Electrodeposits,ed.by Standards volume information, refer to the standard’s Document Summary page on
Sand, 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
B877 − 96 (2018)
3.2.1 base metal, n—any metal other than gold, silver, aqueous PMAsolution is applied to the spot in question using
platinum, palladium, iridium, or rhodium. Typical base metals an applicator. If it contacts base metals from exposed under-
used as underplates or substrates are copper, nickel, tin, lead, plate or substrate, the Mo O will immediately be reduced to
2 3
and their alloys. loweroxides,formingtheintenselycolored,molybdenumblue
complex (heteropoly blue).
3.2.2 defect indications, n—colored droplets resulting from
the reaction between the PMA reagent and the underlying
4.2 This test may not be suitable for some precious metal
metal. alloy coatings that contain significant concentrations of non-
precious metals (base metals) like nickel or copper. (See .)
3.2.3 gross defects, n—those breaks in the coating that
expose relatively large areas of underlying metal to the
4.3 The reagents in this test also react with tin, lead, and
environment. Gross defects include those produced by me-
tin-lead solder.
chanicaldamageandwear,aswellasas-platedlargeporeswith
5. Significance and Use
diameters an order of magnitude greater than intrinsic porosity
and networks of microcracks.
5.1 TheprimarypurposeofthePMAtestistodeterminethe
presenceofmechanicaldamage,wearthrough,andothergross
NOTE 1—Large pores and microcrack networks indicate serious devia-
defects in the coating. Most metallic coatings are intended to
tions from acceptable coating practice (dirty substrates and contaminated
or out-of-balance plating baths). be protective, and the presence of gross defects indicates a
serious reduction of such protection.
3.2.4 intrinsic porosity, n—the normal porosity that is
present, to some degree, in all commercial thin electrodeposits
5.2 Theprotectionaffordedbywellappliedcoatingsmaybe
(precious metal coatings for engineering purposes) that will
diminished by improper handling following plating or as a
generally follow an inverse relationship with thickness.
resultofwearormechanicaldamageduringtestingorwhilein
service. The PMA test can serve to indicate the existence of
NOTE2—Intrinsicporosityisduetosmalldeviationsfromidealplating
such damage.
and surface preparation conditions. Scanning electron microscope (SEM)
studies have shown the diameter of such pores at the plating surface is 1
5.3 Thistestisusedtodetectunderplateandsubstratemetal
to 2 µm so only small areas of underlying metal are exposed to the
exposed through normal wear during relative motions (mating
environment.
of electrical contacts) or through mechanical damage.As such,
3.2.5 measurement area, n—that portion or portions of the
it is a sensitive pass/fail test and, if properly performed, will
surface that is examined for the presence of gross defects or
rapidly detect wear through to base metals or scratches that
mechanical damage and wear through. The measurement area
enter the base metal layers.
shall be indicated on the drawings of the parts or by the
5.4 This test is relatively insensitive to small pores. It is not
provision of suitably marked samples.
designed to be a general porosity test and shall not be used as
3.2.6 metallic coatings, n—include electrodeposits,
such. The detection of pores will depend upon their sizes and
claddings,orothermetalliclayersappliedtothesubstrate.The
the length of time that the reagent remains a liquid.
coating can comprise a single metallic layer or a combination
5.5 This test cannot distinguish degrees of wear through or
of metallic layers (gold over palladium).
whether the wear through is to nickel or copper. Once base
3.2.7 porosity (general), n—thepresenceofanyhole,crack,
metalisexposed,thecoloredmolybdenumcomplexisformed.
or other defect that exposes the underlying metal to the
Whilerelativelysmallareadefects(comparedtotheareaofthe
environment.
droplet) may be seen at the bottom of the drop as tiny colored
3.2.8 underplate, n—a metallic coating layer between the
regions immediately after applying the PMA, any larger areas
substrateandthetopmostmetalliccoating.Thethicknessofan
ofexposedbasemetalwillcausetheentiredroplettoturndark
underplate is usually greater than 1 µm, in contrast to a strike
instantly.
or flash, which is usually thinner.
5.6 The PMA test also detects mechanical damage that
3.2.9 wear through, n—the exposure of underplate or sub-
exposes underplate and substrate metal. Such damage may
strate as a direct result of wear. Wear through is an observable
occur in any postplating operation or even at the end of the
phenomenon.
plating operation. It can often occur in assembly operations
3.2.10 wear track, n—a mark that indicates the path along where plated parts are assembled into larger units by mechani-
which physical contact has been made during a sliding process
cal equipment.
(the mating and unmating of an electrical contact).
5.7 The PMA test identifies the locations of exposed base
metal. The extent and location of these exposed areas may or
4. Summary of Test Method
may not be detrimental to performance. The PMA test is not
4.1 This test method involves the use of a solution of recommended for predictions of product performance, nor is it
intendedtosimulatefieldfailuremechanisms.Forsuchcontact
phosphomolybdic acid (PMA), which is a solid complex of
molybdenumtrioxide,Mo O ,andphosphoricacid,H PO.In performance evaluations, an environmental test known to
2 3 3 4
simulate actual failure mechanisms should be used.
this state, molybdenum is very reactive with many free metals
and may be used to detect exposed underplates and substrate
metals. The part is exposed briefly to fumes of hydrochloric
Van Wazer, J. P., Phosphorous and Its Compounds, Interscience Publishers,
acid to remove oxides in the defect region.Asmall drop of the New York, 1961.
B877 − 96 (2018)
5.8 ThePMAtestisprimarilyintendedfortheevaluationof 9.1.2 Dilute (8%) PMA solution (for Method A):
individual samples rather than large sample lots, since evalu- 9.1.2.1 Placeasmall,clean,anddryglassfunnelintheneck
ations are normally carried out one at a time under the of a clean, dry 10 mL volumetric flask.
microscope (see Section 10). 9.1.2.2 Tare out the weight of the funnel and flask on a
balance.
5.9 This test is destructive. Any parts exposed to the PMA
9.1.2.3 Weigh 0.8 (60.1) g PMA into the flask, using a
test shall not be placed in service.
plastic or glass spatula.
9.1.2.4 Rinse the funnel with distilled or deionized water to
6. Apparatus
drain any adhering PMA into the flask.
6.1 In addition to the normal equipment (beakers, weighing
9.1.2.5 Dilute to mark with deionized water.
balances, funnels, etc.) that are a part of every chemical
9.1.2.6 Place stopper in flask and mix thoroughly. Cloudy
laboratory.
solution will clear after standing 10 to 15 min.
6.2 Microscope, Optical, Stereo, 10 to 30× —It is preferred
9.1.2.7 Pour clear solution into a clean glass bottle and seal
that one eyepiece contain a graduated reticle for measuring the
with glass stopper. Label bottle with PMA concentration and
defect location. The reticle shall be calibrated for the magni-
date of preparation.
ficationatwhichthemicroscopeistobeused,preferably10×.
9.1.2.8 Storebottleinrefrigerator.Solutionmaybeusedfor
one week.
6.3 Lightsource(illuminator)formicroscope,incandescent.
9.1.3 Saturated PMA solution (for Method B):
6.4 Glass volumetric flask, 10 mL.
9.1.3.1 Prepare solution in accordance with 9.1.2.1 –
6.5 Glassbottleofastableshapeandwithglassstopper.The
9.1.2.6,exceptuseapproximately5gofPMAinsteadof0.8g.
bottle opening shall be 2.5 cm (1 in) minimum.An example is
(Filter out sediment, if necessary.)
a 50-mLlow-form weighing bottle or a flask-shaped weighing
9.1.3.2 Mix thoroughly for at least 10 min.
bottle.
NOTE 4—There shall be a small excess of PMA, seen as a sediment in
6.6 Applicators (see 9.2)—Platinum wire, 32 AWG, or the bottom of the flask. This indicates saturation.
disposable glass micropipets, 1 or 0.5 µL size.
9.1.3.3 Pour into a clean bottle and label bottle with
contents and preparation date.
7. Reagents and Materials
9.1.3.4 Solution may be used for one week. Store in
7.1 Phosphomolybdic Acid (PMA)—Crystalline, ACS certi-
refrigerator when not in use.
fied grade.
9.1.4 Hydrochloric acid (for both methods):
9.1.4.1 Fill the special glass bottle (see 6.4) to approxi-
7.2 Concentrated Hydrochloric Acid— ACS analytical re-
mately halfway from the top.
agent (AR) grade or better.
9.1.4.2 Label glass bottle with contents.
8. Specific Safety and Health Precautions
9.1.4.3 Keep stoppered and under a fume hood when not in
use.
8.1 Allthenormalprecautionsshallbeobservedinhandling
thematerialsrequiredforthistest.Thisshallinclude,butisnot 9.2 Preparation of applicators:
limited to, procuring and reviewing Material Safety Data
9.2.1 The applicator shall not react with the PMAsolution.
Sheets that meet the minimum requirements of the OSHA Examples are as follows:
Hazard Communication Standard for all chemicals used in
9.2.1.1 Platinum—Make a small loop using a 32 AWG
cleaning and testing and observing the recommendations platinum wire and an appropriate size mandrel (such as a
given.
needle). Leave a small gap to facilitate release of the PMA
droplet (see Fig. 1).Attach loop to a wooden or plastic handle.
9. Preparations
9.2.1.2 Platinum inoculating loops with handles may be
purchased.Cuttheloopwithaknifetocreateasmallgap(Fig.
9.1 Preparation of solutions:
9.1.1 Two types of PMA solutions can be used with this 1), which will facilitate the release of the PMA droplet.
9.2.1.3 Glass capillary micropipets in the 1-µL size or
method.
9.1.1.1 Method A, the preferred method, uses a dilute 8% smaller.
9.2.2 If a platinum loop is used as the applicator, the loop
solution of PMA in water.
9.1.1.2 Method B, uses a saturated solution of PMA in diameter shall preferably be 1 mm and shall not exceed 2 mm.
The loop diameter is kept small for the following reasons:
water.
NOTE 3—The dilute solution is preferred because it works well with
silver, gold, and palladium coatings, while the saturated solution reacts
withsilvertogivefalseindications.Inaddition,thesaturatedsolutionhas
a tendency to dry up quickly on the test surface before proper evaluations
can be made.
Magnification standards suitable for calibrating opti
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