ASTM B537-70(2002)e1
(Practice)Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
SCOPE
1.1 This practice covers a preferred method for evaluating the condition of electroplated test panels that have been exposed to corrosive environments for test purposes. It is based on experience in use of the method with standard 10- by 15-cm (4- by 6-in.) panels exposed on standard ASTM racks at outdoor test sites in natural atmospheres. It has been used also for rating similar panels that have been subjected to accelerated tests such as those covered by Practice B 117, Method B 287, Method B 368, and Method B 380. Any modifications needed to adapt the method to rating actual production parts are not considered in this practice.
1.2 This practice refers only to decorative-protective coatings that are cathodic to the substrate, typified by nickel/chromium or copper/nickel/chromium on steel or zinc die castings. It is not intended for use with anodic sacrificial coatings such as zinc and cadmium on steel.
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e1
Designation:B537–70 (Reapproved 2002)
Standard Practice for
Rating of Electroplated Panels Subjected to
Atmospheric Exposure
This standard is issued under the fixed designation B537; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Adjunct references were corrected editorially in April 2006.
1. Scope 2.2 ASTM Adjunct:
Dot charts (9 charts, 8 ⁄2 by 11 in.) (9 color photos, 3 by 5
1.1 This practice covers a preferred method for evaluating
in.)
the condition of electroplated test panels that have been
exposedtocorrosiveenvironmentsfortestpurposes.Itisbased
3. Basis of Procedure
onexperienceinuseofthemethodwithstandard10-by15-cm
3.1 The rating method described in this recommended
(4- by 6-in.) panels exposed on standard ASTM racks at
practice is based on the recognition that typical decorative-
outdoor test sites in natural atmospheres. It has been used also
protective deposits such as nickel/chromium, with or without a
forratingsimilarpanelsthathavebeensubjectedtoaccelerated
copper undercoat, have two functions: (1) to protect the
tests such as those covered by PracticeB117, Method B287,
substrate from corrosion and thus prevent degradation of
TestMethodB368,andTestMethodB380.Anymodifications
appearance caused by basis metal corrosion products (for
neededtoadaptthemethodtoratingactualproductionpartsare
example, rust and rust stain); and (2) to itself maintain a
not considered in this practice.
satisfactoryappearance.Althoughthesefunctionsoverlap,they
1.2 This practice refers only to decorative-protective coat-
can be evaluated separately and it is frequently desirable to do
ings that are cathodic to the substrate, typified by nickel/
so. Accordingly, this practice assigns separate ratings to (1)
chromium or copper/nickel/chromium on steel or zinc die
appearance as affected by corrosion of the substrate and (2)
castings. It is not intended for use with anodic sacrificial
appearance as affected by deterioration of the coating itself.
coatings such as zinc and cadmium on steel.
3.2 The rating number assigned to the ability of the coating
2. Referenced Documents to protect the substrate from corrosion is called the “protec-
2 tion” number or rating.
2.1 ASTM Standards:
3.3 The rating number assigned to the inspector’s judgment
B117 Practice for Operating Salt Spray (Fog) Apparatus
3 of the overall appearance of the panel, including all defects
B287 Method of Acetic Acid-Salt Spray (Fog) Testing
caused by the exposure (Note 1), is called the “appearance”
B368 Test Method for Copper-Accelerated Acetic Acid-
number or rating.
Salt Spray (Fog) Testing (CASS Test)
B380 Test Method of Corrosion Testing of Decorative
NOTE 1—Panels that are not “perfect” even before being exposed
Electrodeposited Coatings by the Corrodkote Procedure
should normally be rejected (see Note 4).
3.4 The result of inspecting a panel is recorded as two
numbers separated by a slash (/), the protection number being
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
given first.
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.08.03
3.5 In addition to recording the numerical rating of a panel,
on Decorative Coatings.
the inspector should note the type(s) and severity of defect(s)
Current edition approved Oct. 3, 1970. Originally approved in 1970. Last
contributing to the rating. This may be done by the use of
previous edition approved in 1997 as B537–70 (1997).
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 4
Color reproductions of these photographs are available from ASTM Interna-
the ASTM website.
tional Headquarters. Order Adjunct No. ADJB0537. Original adjunct produced in
Withdrawn.
1987.
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e1
B537–70 (2002)
agreed symbols for the most common defects (Appendix X1) area absolutely necessary for the purpose, preferably not more
and abbreviations for degree or severity of these defects. than 1 cm of a 10- by 15-cm panel.
4. Types of Defects 6. Assignment of Protection Rating
4.1 “Protection” defects include crater rusting (Note 2),
6.1 The numerical rating system is based on the area
pinhole rusting, rust stain, blisters (Note 3), and any other covered by protection defects, by the following equation:
defects that involve basis metal corrosion.
R 53 ~2 2log A! (1)
NOTE 2—“Rusting” or “rust” as used in this document includes
where R=rating and A=percentage of the total area cov-
corrosion products of the substrate and is not confined to iron or steel: the
ered by defects. R is rounded off to the nearest whole number,
white corrosion products of zinc die castings and aluminum, for example,
leading to the tabulation given in Table 1.
are included in this term.
6.1.1 Strict application of the equation given in 6.1 would
NOTE 3—Blistersonplatedzincdiecastingusuallyconnotebasismetal
lead to ratings greater than 10 for panels with extremely small
corrosion;buttheinspector’sjudgmentmayberequiredtodecidewhether
a blister does or does not arise at the substrate-coating interface.
defective areas. Rating 10, accordingly, is arbitrarily assigned
to a panel with no defects, and the equation operates at ratings
4.2 “Appearance” defects include, the addition to those
9 and below.
caused by basis metal corrosion, all defects that detract from
6.1.2 If desired, fractional ratings between 9 and 10 may be
the appearance (that is, the commercial acceptability) of the
assigned to panels judged better than 9 but not perfect.
panel. Typical are: surface pits, “crow’s feet,” crack patterns,
Fractional ratings below 9, although normally not especially
surface stain, and tarnish.
useful, may be assigned if desired.
4.3 Defects developing on exposure that reflect improper
6.2 As an aid in judging the defective area, standards of
preparationorplatingshouldbenotedbutnoattemptshouldbe
comparison, consisting of photographs of panels or of dot
made to rate panels showing major amounts of such defects.
charts are made part of this practice. SeeAppendix X2. These
Peeling of the coating from the substrate, or of one coat from
photographs and charts are 10 by 15 cm (4 by 6 in.) to
another, is the principal such defect.
facilitate comparison with the panel being inspected. The
standardsrepresentasnearlyaspossiblethemaximumamount
5. Preparation for and Manner of Inspection
of corrosion permissible for a given rating; there is a standard
NOTE 4—Itmaybedesirabletoexposepanelsfortesteventhoughthey
foreachrating1through9.Apanelworsethanthestandardfor
are defective in certain respects before exposure. In that case, an
rating 1 would rate 0.
inspection should be made and recorded before the panels are exposed.
6.2.1 The types of corrosion defects normally encountered
5.1 Panels may be inspected on the exposure racks or may
differ according to the type of atmospheric exposure. Typical
be removed to a more suitable location if necessary. Lighting
decorative deposits exposed to marine atmospheres often tend
during inspection should be as nearly uniform as possible;
tofailbycraterrusting,whereasinindustrialatmospheres,they
direct reflection from sun or clouds should be avoided, and
are more likely to exhibit pinpoint rusting; and the latter
various angles of inspection should be tried to ensure that
atmosphere also tends to be more severe with regard to
defects show up.
degradation of the coating system but somewhat less severe
5.2 If the condition of the panels allows, inspection should
with regard to basis metal corrosion. For this reason, the same
be made in the “as-is” condition. If dirt, salt deposits, and so
standard comparison photographs or charts are not suitable for
forth, make it impractical to inspect them, panels may be
use at both types of locations; photographs are more helpful in
spongedwithamildsoapsolutionfollowedbywaterrinse;but
assessing panels exposed to marine atmospheres, whereas dot
no pressure should be exerted in this procedure such as would
charts can be used for industrial locations (Appendix X2).
tend to upgrade the rating by, for example, cleaning off rust or
6.3 In rating any given panel, it is recommended that the
rust stain. Panels should be allowed to dry before inspecting
appropriateseriesofstandardsbeplacedbesideitandthebasis
them.
metal corrosion defects in the panel be matched as nearly as
5.3 Defects to be noted and taken into account in rating
possible with one of the standards. If the panel is somewhat
panelsincludeonlythosethatcanbeseenwiththeunaidedeye
better than standard ( X) but not as good as standard (X+1)it
(Note 5) at normal reading distance.
NOTE 5—“Unaided eye” includes wearing of correctional glasses if the
TABLE 1 Protection Rating Versus Area of Defect
inspector normally wears them.
Area of Defect (in percent) Rating
5.3.1 Optical aids may be used to identify or study defects
once they are found by unaided eye inspection.
To 0.1 9
5.4 Edge defects, occurring within 6.5 mm ( ⁄4 in.) of the
0.1to0.25 8
edges of a
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