ASTM B537-70(2013)
(Practice)Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
ABSTRACT
This practice covers the recommended method for rating the condition of electroplated test panels subjected to corrosive environments for test purposes. This method is used with standard-sized panels exposed on standard ASTM racks at outdoor test sites in both natural atmospheres and accelerated test conditions. This practice refers only to decorative-protective coatings that are cathodic to the substrate such as nickel/chromium or copper/nickel/chromium on steel or zinc die castings, and is not intended for use with anodic sacrificial coatings such as zinc and cadmium on steel. Any modifications needed to adapt the method to rating actual production parts are not considered here. Panels shall be assigned separate rating numbers based on the ability of the coating to protect the substrate from corrosion (protection rating), and the overall appearance of panels as affected by deterioration of the coating itself (appearance rating). Accordingly, rating numbers shall be derived from the type of defect that exists, that is: (1) protection defects, which include crater rusting, pinhole rusting, rust stains, blisters, and other defects that involve basis metal corrosion; and (2) appearance defects, which include surface pits, "crow's feet," crack patterns, surface stains, tarnishes, and other defects that detract from commercial acceptability as to appearance. Inspection should be made in the as-is condition, and defects to be taken into account are only those that can be seen with the unaided eye at normal reading distance.
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 B117, Method B287, Test Method B368, and Test Method B380. 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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Designation: B537 − 70 (Reapproved 2013)
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 (´) indicates an editorial change since the last revision or reapproval.
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 Practice B117, Method B287,
substrate from corrosion and thus prevent degradation of
Test Method B368, and Test Method B380.Any modifications
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
to protect the substrate from corrosion is called the “protec-
2. Referenced Documents
tion” number or rating.
2.1 ASTM Standards:
3.3 The rating number assigned to the inspector’s judgment
B117Practice for Operating Salt Spray (Fog) Apparatus
of the overall appearance of the panel, including all defects
B287Method of Acetic Acid-Salt Spray (Fog) Testing
caused by the exposure (Note 1), is called the “appearance”
(Withdrawn 1987)
number or rating.
B368Test Method for Copper-AcceleratedAceticAcid-Salt
Spray (Fog) Testing (CASS Test)
NOTE 1—Panels that are not “perfect” even before being exposed
B380Test Method for Corrosion Testing of Decorative should normally be rejected (see Note 4).
Electrodeposited Coatings by the Corrodkote Procedure
3.4 The result of inspecting a panel is recorded as two
numbers separated by a slash (/), the protection number being
1 given first.
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.05 on
3.5 In addition to recording the numerical rating of a panel,
Decorative Coatings.
the inspector should note the type(s) and severity of defect(s)
Current edition approved Dec. 1, 2013. Published December 2013. Originally
contributing to the rating. This may be done by the use of
approved in 1970. Last previous edition approved in 2007 as B537–70 (2007).
DOI: 10.1520/B0537-70R13.
agreed symbols for the most common defects (Appendix X1)
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and abbreviations for degree or severity of these defects.
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. Color reproductions of these photographs are available from ASTM Interna-
The last approved version of this historical standard is referenced on tional Headquarters. Order Adjunct No. ADJB0537. Original adjunct produced in
www.astm.org. 1987.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B537 − 70 (2013)
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 5 3 2 2 logA (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.
NOTE3—Blistersonplatedzincdiecastingusuallyconnotebasismetal
6.1.1 Strict application of the equation given in 6.1 would
corrosion;buttheinspector’sjudgmentmayberequiredtodecidewhether
lead to ratings greater than 10 for panels with extremely small
a blister does or does not arise at the substrate-coating interface.
defective areas. Rating 10, accordingly, is arbitrarily assigned
4.2 “Appearance” defects include, the addition to those
to a panel with no defects, and the equation operates at ratings
caused by basis metal corrosion, all defects that detract from
9 and below.
the appearance (that is, the commercial acceptability) of the
6.1.2 If desired, fractional ratings between 9 and 10 may be
panel. Typical are: surface pits, “crow’s feet,” crack patterns,
assigned to panels judged better than 9 but not perfect.
surface stain, and tarnish.
Fractional ratings below 9, although normally not especially
useful, may be assigned if desired.
4.3 Defects developing on exposure that reflect improper
preparationorplatingshouldbenotedbutnoattemptshouldbe
6.2 As an aid in judging the defective area, standards of
made to rate panels showing major amounts of such defects.
comparison, consisting of photographs of panels or of dot
Peeling of the coating from the substrate, or of one coat from
charts are made part of this practice. See Appendix X2. These
another, is the principal such defect.
photographs and charts are 10 by 15 cm (4 by 6 in.) to
facilitate comparison with the panel being inspected. The
5. Preparation for and Manner of Inspection
standardsrepresentasnearlyaspossiblethemaximumamount
NOTE4—Itmaybedesirabletoexposepanelsfortesteventhoughthey
of corrosion permissible for a given rating; there is a standard
are defective in certain respects before exposure. In that case, an
foreachrating1through9.Apanelworsethanthestandardfor
inspection should be made and recorded before the panels are exposed.
rating 1 would rate 0.
5.1 Panels may be inspected on the exposure racks or may
6.2.1 The types of corrosion defects normally encountered
be removed to a more suitable location if necessary. Lighting
differ according to the type of atmospheric exposure. Typical
during inspection should be as nearly uniform as possible;
decorative deposits exposed to marine atmospheres often tend
direct reflection from sun or clouds should be avoided, and
tofailbycraterrusting,whereasinindustrialatmospheres,they
various angles of inspection should be tried to ensure that
are more likely to exhibit pinpoint rusting; and the latter
defects show up.
atmosphere also tends to be more severe with regard to
5.2 If the condition of the panels allows, inspection should
degradation of the coating system but somewhat less severe
be made in the “as-is” condition. If dirt, salt deposits, and so
with regard to basis metal corrosion. For this reason, the same
forth, make it impractical to inspect them, panels may be
standard comparison photographs or charts are not suitable for
spongedwithamildsoapsolutionfollowedbywaterrinse;but
use at both types of locations; photographs are more helpful in
no pressure should be exerted in this procedure such as would
assessing panels exposed to marine atmospheres, whereas dot
tend to upgrade the rating by, for example, cleaning off rust or
charts can be used for industrial locations (Appendix X2).
rust stain. Panels should be allowed to dry before inspecting
6.3 In rating any given panel, it is recommended that the
them.
appropriateseriesofstandardsbeplacedbesideitandthebasis
5.3 Defects to be noted and taken into account in rating
metal corrosion defects in the panel be matched as nearly as
panelsincludeonlythosethatcanbeseenwiththeunaidedeye
possible with one of the standards. If the panel is somewhat
(Note 5) at normal reading distance.
better than standard (X) but not as good as standard (X+1)it
israted(X);ifsomewhatworsethanstandard(X)butnotasbad
NOTE 5—“Unaided eye” includes wearing of correctional glasses if the
inspector normally wears them.
5.3.1 Optical aids may be used to identify or study defects
once they are found by unaided eye inspection.
TABLE 1 Protection Rating Versus Area of Defect
5.4 Edge defects, occurring within 6.5 mm ( ⁄4 in.) of the
Area of Defect (in percent) Rating
edges of a panel, may be noted in the description but are not
To 0.1 9
counted in arriving at the numerical
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