ASTM B651-83(2015)
(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
4.1 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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Designation: B651 − 83 (Reapproved 2015)
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 microscope, and interference microscope). The values are
compared to dimensions and numbers of corrosion sites
1.1 This test method provides a means for measuring the
obtained from other specimens.
average dimensions and number of corrosion sites in an
electroplated decorative nickel plus chromium or copper plus
4. Significance and Use
nickel plus chromium coating on steel after the coating has
4.1 Different electroplating systems can be corroded under
beensubjectedtocorrosiontests.Thistestmethodisusefulfor
thesameconditionsforthesamelengthoftime.Differencesin
comparing the relative corrosion resistances of different elec-
the average values of the radius or half-width or of penetration
troplating systems and for comparing the relative corrosivities
into an underlying metal layer are significant measures of the
of different corrosive environments. The numbers and sizes of
relative corrosion resistance of the systems. Thus, if the pit
corrosion sites are related to deterioration of appearance.
radii are substantially higher on samples with a given electro-
Penetrationoftheelectroplatedcoatingsleadstoappearanceof
plating system, when compared to other systems, a tendency
basis metal corrosion products.
for earlier failure of the former by formation of visible pits is
1.2 The values stated in SI units are to be regarded as the
indicated. If penetration into the semi-bright nickel layer is
standard.
substantially higher, a tendency for earlier failure by corrosion
1.3 This standard does not purport to address all of the
of basis metal is evident.
safety concerns, if any, associated with its use. It is the
5. Apparatus
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5.1 Double-Beam Interference Microscope (lateral magnifi-
bility of regulatory limitations prior to use.
cation about 100×), capable of producing, with white light, a
visible group of interference fringes, and equipped with a
2. Referenced Documents
calibrated fine focus and a graduated bifilar (movable cross
2.1 ASTM Standards:
hair) eyepiece.
B487Test Method for Measurement of Metal and Oxide
5.2 Magnifier or Microscope (10× to 20×), with light
Coating Thickness by Microscopical Examination of
source.
Cross Section
5.3 Rule, graduated in millimetres, and a scriber for pro-
3. Summary of Test Method 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 500×,
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.
surface, are determined using optical aids (magnifier,
5.5 Equipmentformountingandpolishingofspecimensfor
microscopical cross-sectional measurements.
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
6. Specimen Preparation
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.05 on
Decorative Coatings.
6.1 Clean the corroded specimen surface with an agent or
Current edition approved March 1, 2015. Published April 2015. Originally
agents that remove soil and corrosion products, but do not
approved in 1978. Last previous edition approved in 2010 as B651–83 (2010).
DOI: 10.1520/B0651-83R15.
significantlychangethesurfaceofthecorrosionsites.Scouring
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
powder may be used to remove insoluble corrosion products,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
organic solvent to remove road tar, water accompanied by
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. gentleabrasionwithaclothtoremovelightlyadherentsoil,etc.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B651 − 83 (2015)
6.2 Mask with paint or tape that portion of the specimen 7.1.3 For surfaces with more than about five cracks per
surface on which no measurements of pits or cracks will be millimetre, count the number of cracks on the surface image
made. Alternatively, a gasketed cell pressed onto the surface that cross a 100× microscope reticle line of known length.
may be used. The opening in the gasket will define the area to 7.1.4 For a surface with fewer than about five cracks per
be stripped. millimetre, lightly scribe a straight line up to 50 mm long on
the specimen surface. Using a magnifier or, if necessary, a
NOTE 1—If pitted, the area selected for measurement should contain at
100× microscope, count the number of cracks in a known
least 100 pits or be as large as 50 by 50 mm. If the area contains cracks,
length of line, or all the cracks in 50 mm length, whichever
the location for measurement should contain at least 100 cracks, or be at
least 50 mm long.
comes first.
6.3 Strip the chromium anodically at 6 to 8 V in a solution
NOTE3—Ifthecrackstendtobeoriented,scribethelineapproximately
containing about 50 g/L of sodium carbonate (Na CO ).
perpendicular to the predominant crack direction.
2 3
6.4 Remove masking material, if desired. 7.2 Calculate the number of pits as pits per square
millimetre, or the number of cracks as cracks per millimetre.
NOTE 2—If tape was employed for masking, its removal is recom-
Enter result in Table 1 under “pit density” or “crack density.”
mended. When the specimen rests on tape, it will allow the specimen to
settle slowly. This gradual movement interferes with measurements of
8. Determination of Mean Dimensions of Pits or Cracks
penetration with the interference microscope.
8.1 Observe one pit or crack with the interference micro-
7. Procedure for Determination of Average Number of
scope.
Pits or Cracks
8.1.1 Using the bifilar eyepiece, count the number of eye-
piece scale units occupied by the major diameter of the pit, or
7.1 Using the 10× to 20× magnifier, count the number of
bythewidthofthecrack.Ifthecrackwidthvaries,orifthepit
pitsinaknownareaorthenumberofcracksintersectingaline
outline is irregular, estimate the average. Enter “width” value
of known length. Where uncertainty exists as to whether
in Table 1.
localized blemishes are corrosion sites when the magnifier is
8.1.2 Adjust the elevation of the microscope tube so that
employed, use the 100× microscope for
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B651 − 83 (Reapproved 2010) B651 − 83 (Reapproved 2015)
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. 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.
2. Referenced Documents
2.1 ASTM Standards:
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
3. Summary of Test Method
3.1 The depths and diameter of corrosion pits or the widths of corrosion crevices, and the number of pits per square millimetre
or crevices per linear millimetre on a specimen surface, are determined using optical aids (magnifier, microscope, and interference
microscope). The values are compared to dimensions and numbers of corrosion sites obtained from other specimens.
4. Significance and Use
4.1 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.
5. Apparatus
5.1 Double-Beam Interference Microscope (lateral magnification about 100×), capable of producing, with white light, a visible
group of interference fringes, and equipped with a calibrated fine focus and a graduated bifilar (movable cross hair) eyepiece.
5.2 Magnifier or Microscope (10× to 20×), with light source.
5.3 Rule, graduated in millimetres, and a scriber for producing visible lines on the specimen surface.
5.4 Microscope, with a magnification capability of 500×, equipped with a bifilar eyepiece, for making measurements on opaque
surfaces.
This test method is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.05 on
Decorative Coatings.
Current edition approved Nov. 1, 2010March 1, 2015. Published November 2010April 2015. Originally approved in 1978. Last previous edition approved in 20062010
as B651 – 83 (2006).(2010). DOI: 10.1520/B0651-83R10.10.1520/B0651-83R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM 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 (2015)
5.5 Equipment for mounting and polishing of specimens for microscopical cross-sectional measurements.
6. Specimen Preparation
6.1 Clean the corroded specimen surface with an agent or agents that remove soil and corrosion products, but do not
significantly change the surface of the corrosion sites. Scouring powder may be used to remove insoluble corrosion products,
organic solvent to remove road tar, water accompanied by gentle abrasion with a cloth to remove lightly adherent soil, etc.
6.2 Mask with paint or tape that portion of the specimen surface on which no measurements of pits or cracks will be made.
Alternatively, a gasketed cell pressed onto the surface may be used. The opening in the gasket will define the area to be stripped.
NOTE 1—If pitted, the area selected for measurement should contain at least 100 pits or be as large as 50 by 50 mm. If the area contains cracks, the
location for measurement should contain at least 100 cracks, or be at least 50 mm long.
6.3 Strip the chromium anodically at 6 to 8 V in a solution containing about 50 g/L of sodium carbonate (Na CO ).
2 3
6.4 Remove masking material, if desired.
NOTE 2—If tape was employed for masking, its removal is recommended. When the specimen rests on tape, it will allow the specimen to settle slowly.
This gradual movement interferes with measurements of penetration with the interference microscope.
7. Procedure for Determination of Average Number of Pits or Cracks
7.1 Using the 10× to 20× magnifier, count the number of pits in a known area or the number of cracks intersecting a line of
known length. Where uncertainty exists as to whether localized blemishes are corrosion sites when the magnifier is employed, use
the 100× microscope for verification. Extreme accuracy is not necessary; values within 610 % of the true value are adequate.
7.1.1 For surfaces where the number of pits is more than about 1000/cm , count the pits bounded by lines seen in the eyepiece
reticle of the 100× microscope enclosing a known area of specimen surface (probably about 0.5 mm ).
7.1.2 For surfaces where the number of pits is less than about 1000/cm , lightly scribe lines 10 mm or less apart to form a
rectilinear grid on the surface. Count the number of pits within a scribed area, by using the magnifier, or the 100× microscope,
whichever has the necessary resolution to assure pit identification. Determine the area that contains about 100 pits, or, if the area
2 2
exceeds 25 cm , count the number of pits in a 25 cm area.
7.1.3 For surfaces with more than about five cracks per millimetre, count the number of cracks on the surface image that cross
a 100× microscope reticle line of known length.
7.1.4 For a surface with fewer than about five cracks per millimetre, lightly scribe a straight line up to 50 mm long on the
specimen su
...
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