ASTM B537-70(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
Designation: B 537 – 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.
1. Scope satisfactoryappearance.Althoughthesefunctionsoverlap,they
can be evaluated separately and it is frequently desirable to do
1.1 This practice covers a preferred method for evaluating
so. Accordingly, this practice assigns separate ratings to (1)
the condition of electroplated test panels that have been
appearance as affected by corrosion of the substrate and (2)
exposedtocorrosiveenvironmentsfortestpurposes.Itisbased
appearance as affected by deterioration of the coating itself.
onexperienceinuseofthemethodwithstandard10-by15-cm
3.2 The rating number assigned to the ability of the coating
(4- by 6-in.) panels exposed on standard ASTM racks at
to protect the substrate from corrosion is called the “protec-
outdoor test sites in natural atmospheres. It has been used also
tion” number or rating.
forratingsimilarpanelsthathavebeensubjectedtoaccelerated
3.3 The rating number assigned to the inspector’s judgment
tests such as those covered by Practice B117, Method B287,
of the overall appearance of the panel, including all defects
Method B368, and Method B380. Any modifications needed
caused by the exposure (Note 1), is called the “appearance”
to adapt the method to rating actual production parts are not
number or rating.
considered in this practice.
1.2 This practice refers only to decorative-protective coat-
NOTE 1—Panels that are not “perfect” even before being exposed
ings that are cathodic to the substrate, typified by nickel/
should normally be rejected (see Note 4).
chromium or copper/nickel/chromium on steel or zinc die
3.4 The result of inspecting a panel is recorded as two
castings. It is not intended for use with anodic sacrificial
numbers separated by a slash (/), the protection number being
coatings such as zinc and cadmium on steel.
given first.
3.5 In addition to recording the numerical rating of a panel,
2. Referenced Documents
the inspector should note the type(s) and severity of defect(s)
2.1 ASTM Standards:
contributing to the rating. This may be done by the use of
B117 Practice for Operating Salt Spray (Fog) Apparatus
agreed symbols for the most common defects (Appendix X1)
B287 Method of Acetic Acid-Salt Spray (Fog) Testing
and abbreviations for degree or severity of these defects.
B368 Method for Copper-Accelerated Acetic Acid-Salt
Spray (Fog) Testing (CASS Test)
4. Types of Defects
B380 Method of Corrosion Testing of Decorative Elec-
4.1 “Protection” defects include crater rusting (Note 2),
trodeposited Coatings by the Corrodkote Procedure
pinhole rusting, rust stain, blisters (Note 3), and any other
defects that involve basis metal corrosion.
3. Basis of Procedure
NOTE 2—“Rusting” or “rust” as used in this document includes
3.1 The rating method described in this recommended
corrosion products of the substrate and is not confined to iron or steel: the
practice is based on the recognition that typical decorative-
white corrosion products of zinc die castings and aluminum, for example,
protective deposits such as nickel/chromium, with or without a
are included in this term.
copper undercoat, have two functions: (1) to protect the
NOTE 3—Blistersonplatedzincdiecastingusuallyconnotebasismetal
substrate from corrosion and thus prevent degradation of
corrosion;buttheinspector’sjudgmentmayberequiredtodecidewhether
appearance caused by basis metal corrosion products (for a blister does or does not arise at the substrate-coating interface.
example, rust and rust stain); and (2) to itself maintain a
4.2 “Appearance” defects include, the addition to those
caused by basis metal corrosion, all defects that detract from
the appearance (that is, the commercial acceptability) of the
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
panel. Typical are: surface pits, “crow’s feet,” crack patterns,
and Inorganic Coatingsand is the direct responsibility of Subcommittee
B08.08.03on Decorative Coatings.
surface stain, and tarnish.
Current edition approved Oct. 3, 1970.
4.3 Defects developing on exposure that reflect improper
Annual Book of ASTM Standards, Vol 03.02.
3 preparationorplatingshouldbenotedbutnoattemptshouldbe
Discontinued 1988 see 1987 Annual Book of ASTM Standards, Vol 02.05.
made to rate panels showing major amounts of such defects.
Annual Book of ASTM Standards, Vol 02.05.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
B 537
TABLE 1 Protection Rating Versus Area of Defect
Peeling of the coating from the substrate, or of one coat from
another, is the principal such defect. Area of Defect (in percent) Rating
To 0.1 9
5. Preparation for and Manner of Inspection
0.1to0.25 8
NOTE 4—Itmaybedesirabletoexposepanelsfortesteventhoughthey 0.25 to 0.5 7
0.5to1.0 6
are defective in certain respects before exposure. In that case, an
1.0to2.5 5
inspection should be made and recorded before the panels are exposed.
2.5to5 4
5.1 Panels may be inspected on the exposure racks or may 5to10 3
10 to 25 2
be removed to a more suitable location if necessary. Lighting
25 to 50 1
during inspection should be as nearly uniform as possible;
>50 0
direct reflection from sun or clouds should be avoided, and
various angles of inspection should be tried to ensure that
defects show up.
5.2 If the condition of the panels allows, inspection should
charts are made part of this practice. SeeAppendix X2. These
,
be made in the “as-is” condition. If dirt, salt deposits, and so
photographs and charts are 10 by 15 cm (4 by 6 in.) to
forth, make it impractical to inspect them, panels may be
facilitate comparison with the panel being inspected. The
spongedwithamildsoapsolutionfollowedbywaterrinse;but
standards represent as nearly as possible the maximum amount
no pressure should be exerted in this procedure such as would
of corrosion permissible for a given rating; there is a standard
tend to upgrade the rating by, for example, cleaning off rust or
foreachrating1through9.Apanelworsethanthestandardfor
rust stain. Panels should be allowed to dry before inspecting
rating 1 would rate 0.
them.
6.2.1 The types of corrosion defects normally encountered
5.3 Defects to be noted and taken into account in rating
differ according to the type of atmospheric exposure. Typical
panelsincludeonlythosethatcanbeseenwiththeunaidedeye
decorative deposits exposed to marine atmospheres often tend
(Note 5) at normal reading distance.
tofailbycraterrusting,whereasinindustrialatmospheres,they
are more likely to exhibit pinpoint rusting; and the latter
NOTE 5—“Unaided eye” includes wearing of correctional glasses if the
atmosphere also tends to be more severe with regard to
inspector normally wears them.
degradation of the coating system but somewhat less severe
5.3.1 Optical aids may be used to identify or study defects
with regard to basis metal corrosion. For this reason, the same
once they are found by unaided eye inspection.
standard comparison photographs or charts are not suitable for
5.4 Edge defects, occurring within 6.5 mm ( ⁄4 in.) of the
use at both types of locations; photographs are more helpful in
edges of a panel, may be noted in the description but are not
assessing panels exposed to marine atmospheres, whereas dot
counted in arriving at the numerical rating. Similarly contact
charts can be used for industrial locations (Appendix X2).
and rack marks, mounting holes, and so forth, should be
6.3 In rating any given panel, it is recommended that the
disregarded.
appropriateseriesofstandardsbeplacedbesideitandthebasis
5.5 Rubbing, polishing, and so forth, of the surface of the
metal corrosion defects in the panel be matched as nearly as
panel may be desirable to study one or another aspect of its
possible with one of the standards. If the panel is somewhat
condition. Such procedure shall be confined to the minimum
better than standard ( X) but not as good as standard (X+1)it
area absolutely necessary for the purpose, preferably not more
israted(X);ifsomewhatworsethanstandard(X)butnotasbad
than 1 cm of a 10- by 15-cm panel.
asstandard(X−1)itisrated(X−1).Attheinspector’soption,
decimal fractional ratings may be assigned.
6. Assignment of Protection Rating
6.3.1 If a large group of panels is being inspected at one
6.1 The numerical rating system is based on the area
time, it is recommended that the panels be assessed individu-
covered by protection defects, by the following equation:
ally as in 6.3; but when the entire group has been rated, the
R 53 ~2 2log A! (1) ratings should be reviewed to make sure that ratings assigned
actually reflect the relative merits of the panels. This acts as a
where R=rating and A=percentage of the total area cov-
check on individual ratings and aids in ensuring that the
ered by defects. R is rounded off to the nearest whole number,
inspector’s judgment or frame of reference has not changed
leading to the tabulation given in Table 1.
duringthecourseoftheinspection,owingtofatigue,changein
6.1.1 Strict application of the equation given in 6.1 would
lightingconditions,hastetofinishthejob,orothercauses.One
lead to ratings greater than 10 for panels with extremely small
method of facilitating this
...