ASTM B651-83(2006)
(Test Method)Standard Test Method for Measurement of Corrosion Sites in Nickel Plus Chromium or Copper Plus Nickel Plus Chromium Electroplated Surfaces with Double-Beam Interference Microscope
Standard Test Method for Measurement of Corrosion Sites in Nickel Plus Chromium or Copper Plus Nickel Plus Chromium Electroplated Surfaces with Double-Beam Interference Microscope
SIGNIFICANCE AND USE
Different electroplating systems can be corroded under the same conditions for the same length of time. Differences in the average values of the radius or half-width or of penetration into an underlying metal layer are significant measures of the relative corrosion resistance of the systems. Thus, if the pit radii are substantially higher on samples with a given electroplating system, when compared to other systems, a tendency for earlier failure of the former by formation of visible pits is indicated. If penetration into the semi-bright nickel layer is substantially higher, a tendency for earlier failure by corrosion of basis metal is evident.
SCOPE
1.1 This test method provides a means for measuring the average dimensions and number of corrosion sites in an electroplated decorative nickel plus chromium or copper plus nickel plus chromium coating on steel after the coating has been subjected to corrosion tests. This test method is useful for comparing the relative corrosion resistances of different electroplating systems and for comparing the relative corrosivities of different corrosive environments. The numbers and sizes of corrosion sites are related to deterioration of appearance. Penetration of the electroplated coatings leads to appearance of basis metal corrosion products.
1.2 The values stated in SI units are to be regarded as the 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.
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Standards Content (Sample)
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Designation:B651–83 (Reapproved 2006)
Standard Test Method for
Measurement of Corrosion Sites in Nickel Plus Chromium
or Copper Plus Nickel Plus Chromium Electroplated
Surfaces with Double-Beam Interference Microscope
This standard is issued under the fixed designation B651; 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 surface, are determined using optical aids (magnifier, micro-
scope, and interference microscope). The values are compared
1.1 This test method provides a means for measuring the
to dimensions and numbers of corrosion sites obtained from
average dimensions and number of corrosion sites in an
other specimens.
electroplated decorative nickel plus chromium or copper plus
nickel plus chromium coating on steel after the coating has
4. Significance and Use
beensubjectedtocorrosiontests.Thistestmethodisusefulfor
4.1 Different electroplating systems can be corroded under
comparing the relative corrosion resistances of different elec-
thesameconditionsforthesamelengthoftime.Differencesin
troplating systems and for comparing the relative corrosivities
the average values of the radius or half-width or of penetration
of different corrosive environments. The numbers and sizes of
into an underlying metal layer are significant measures of the
corrosion sites are related to deterioration of appearance.
relative corrosion resistance of the systems. Thus, if the pit
Penetrationoftheelectroplatedcoatingsleadstoappearanceof
radii are substantially higher on samples with a given electro-
basis metal corrosion products.
plating system, when compared to other systems, a tendency
1.2 The values stated in SI units are to be regarded as the
for earlier failure of the former by formation of visible pits is
standard.
indicated. If penetration into the semi-bright nickel layer is
1.3 This standard does not purport to address all of the
substantially higher, a tendency for earlier failure by corrosion
safety concerns, if any, associated with its use. It is the
of basis metal is evident.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 Double-Beam Interference Microscope (lateral magni-
fication about 1003), capable of producing, with white light, a
2. Referenced Documents
2 visible group of interference fringes, and equipped with a
2.1 ASTM Standards:
calibrated fine focus and a graduated bifilar (movable cross
B487 Test Method for Measurement of Metal and Oxide
hair) eyepiece.
CoatingThicknessbyMicroscopicalExaminationofCross
5.2 Magnifier or Microscope (103 to 203), with light
Section
source.
3. Summary of Test Method 5.3 Rule, graduated in millimetres, and a scriber for pro-
ducing visible lines on the specimen surface.
3.1 The depths and diameter of corrosion pits or the widths
5.4 Microscope, with a magnification capability of 5003,
of corrosion crevices, and the number of pits per square
equipped with a bifilar eyepiece, for making measurements on
millimetre or crevices per linear millimetre on a specimen
opaque surfaces.
5.5 Equipmentformountingandpolishingofspecimensfor
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
microscopical cross-sectional measurements.
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.08.03
on Decorative Coatings.
6. Specimen Preparation
Current edition approved April 1, 2006. Published April 2006. Originally
approved in 1978. Last previous edition approved in 2001 as B651–83 (2001). 6.1 Clean the corroded specimen surface with an agent or
DOI: 10.1520/B0651-83R06.
agents that remove soil and corrosion products, but do not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
significantlychangethesurfaceofthecorrosionsites.Scouring
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
powder may be used to remove insoluble corrosion products,
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.
B651–83 (2006)
organic solvent to remove road tar, water accompanied by pit identification. Determine the area that contains about 100
gentleabrasionwithaclothtoremovelightlyadherentsoil,etc. pits, or, if the area exceeds 25 cm , count the number of pits in
a 25-cm area.
6.2 Mask with paint or tape that portion of the specimen
7.1.3 For surfaces with more than about 5 cracks per
surface on which no measurements of pits or cracks will be
made. Alternatively, a gasketed cell pressed onto the surface millimetre, count the number of cracks on the surface image
that cross a 1003 microscope reticle line of known length.
may be used. The opening in the gasket will define the area to
be stripped. 7.1.4 For a surface with fewer than about 5 cracks per
millimetre, lightly scribe a straight line up to 50 mm long on
NOTE 1—If pitted, the area selected for measurement should contain at
the specimen surface. Using a magnifier or, if necessary, a
least 100 pits or be as large as 50 by 50 mm. If the area contains cracks,
1003 microscope, count the number of cracks in a known
the location for measurement should contain at least 100 cracks, or be at
length of line, or all the cracks in 50-mm length, whichever
least 50 mm long.
comes first.
6.3 Strip the chromium anodically at 6 to 8 V in a solution
NOTE 3—Ifthecrackstendtobeoriented,scribethelineapproximately
containing about 50 g/L of sodium carbonate (Na CO ).
2 3
perpendicular to the predominant crack direction.
6.4 Remove masking material, if desired.
7.2 Calculate the number of pits as pits per square millime-
NOTE 2—If tape was employed for masking, its removal is recom-
tre, or the number of cracks as cracks per millimetre. Enter
mended. When the specimen rests on tape, it will allow the specimen to
result in Table 1 under “pit density” or “crack density.”
settle slowly. This gradual movement interferes with measurements of
penetration with the interference microscope.
8. Determination of Mean Dimensions of Pits or Cracks
7. Procedure for Determination of Average Number of
8.1 Observe one pit or crack with the interference micro-
Pits or Cracks
scope.
7.1 Using the 103 to 203 magnifier, count the number of
8.1.1 Using the bifilar eyepiece, count the number of eye-
pitsinaknownareaorthenumberofcracksintersectingaline
piece scale units occupied by the major diameter of the pit, or
of known length. Where uncertainty exists as to whether
bythewidthofthecrack.Ifthecrackwidthvaries,orif
...
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