ASTM B537-70(1997)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 537 – 70 (Reapproved 1997)
Standard Practice for
Rating of Electroplated Panels Subjected to
Atmospheric Exposure
This standard is issued under the fixed designation B 537; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope satisfactory appearance. Although these functions overlap, 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)
exposed to corrosive environments for test purposes. It is based
appearance as affected by deterioration of the coating itself.
on experience in use of the method with standard 10- by 15-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.
for rating similar panels that have been subjected to accelerated
3.3 The rating number assigned to the inspector’s judgment
tests such as those covered by Practice B 117, Method B 287,
of the overall appearance of the panel, including all defects
Method B 368, and Method B 380. 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
B 117 Practice for Operating Salt Spray (Fog) Apparatus
agreed symbols for the most common defects (Appendix X1)
B 287 Method of Acetic Acid-Salt Spray (Fog) Testing
and abbreviations for degree or severity of these defects.
B 368 Method for Copper-Accelerated Acetic Acid-Salt
Spray (Fog) Testing (CASS Test)
4. Types of Defects
B 380 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—Blisters on plated zinc die casting usually connote basis metal
substrate from corrosion and thus prevent degradation of
corrosion; but the inspector’s judgment may be required to decide whether
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 Coatings and is the direct responsibility of Subcommittee B08.08.03
surface stain, and tarnish.
on Decorative Coatings.
4.3 Defects developing on exposure that reflect improper
Current edition approved Oct. 3, 1970.
Annual Book of ASTM Standards, Vol 03.02.
preparation or plating should be noted but no attempt should be
Discontinued 1988—Replaced by G85; see 1987 Annual Book of ASTM
made to rate panels showing major amounts of such defects.
Standards, Vol 02.05.
4 Peeling of the coating from the substrate, or of one coat from
Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
B 537
another, is the principal such defect. 6.1.1 Strict application of the equation given in 6.1 would
lead to ratings greater than 10 for panels with extremely small
5. Preparation for and Manner of Inspection
defective areas. Rating 10, accordingly, is arbitrarily assigned
to a panel with no defects, and the equation operates at ratings
NOTE 4—It may be desirable to expose panels for test even though they
are defective in certain respects before exposure. In that case, an 9 and below.
inspection should be made and recorded before the panels are exposed.
6.1.2 If desired, fractional ratings between 9 and 10 may be
assigned to panels judged better than 9 but not perfect.
5.1 Panels may be inspected on the exposure racks or may
Fractional ratings below 9, although normally not especially
be removed to a more suitable location if necessary. Lighting
useful, may be assigned if desired.
during inspection should be as nearly uniform as possible;
6.2 As an aid in judging the defective area, standards of
direct reflection from sun or clouds should be avoided, and
comparison, consisting of photographs of panels or of dot
various angles of inspection should be tried to ensure that
charts are made part of this practice. See Appendix X2. These
defects show up.
,
5 6
photographs and charts are 10 by 15 cm (4 by 6 in.) to
5.2 If the condition of the panels allows, inspection should
facilitate comparison with the panel being inspected. The
be made in the “as-is” condition. If dirt, salt deposits, and so
standards represent as nearly as possible the maximum amount
forth, make it impractical to inspect them, panels may be
of corrosion permissible for a given rating; there is a standard
sponged with a mild soap solution followed by water rinse; but
for each rating 1 through 9. A panel worse than the standard for
no pressure should be exerted in this procedure such as would
rating 1 would rate 0.
tend to upgrade the rating by, for example, cleaning off rust or
6.2.1 The types of corrosion defects normally encountered
rust stain. Panels should be allowed to dry before inspecting
differ according to the type of atmospheric exposure. Typical
them.
decorative deposits exposed to marine atmospheres often tend
5.3 Defects to be noted and taken into account in rating
to fail by crater rusting, whereas in industrial atmospheres, they
panels include only those that can be seen with the unaided eye
are more likely to exhibit pinpoint rusting; and the latter
(Note 5) at normal reading distance.
atmosphere also tends to be more severe with regard to
NOTE 5—“Unaided eye” includes wearing of correctional glasses if the
degradation of the coating system but somewhat less severe
inspector normally wears them.
with regard to basis metal corrosion. For this reason, the same
5.3.1 Optical aids may be used to identify or study defects
standard comparison photographs or charts are not suitable for
once they are found by unaided eye inspection.
use at both types of locations; photographs are more helpful in
5.4 Edge defects, occurring within 6.5 mm ( ⁄4 in.) of the
assessing panels exposed to marine atmospheres, whereas dot
edges of a panel, may be noted in the description but are not
charts can be used for industrial locations (Appendix X2).
counted in arriving at the numerical rating. Similarly contact
6.3 In rating any given panel, it is recommended that the
and rack marks, mounting holes, and so forth, should be
appropriate series of standards be placed beside it and the basis
disregarded.
metal corrosion defects in the panel be matched as nearly as
5.5 Rubbing, polishing, and so forth, of the surface of the
possible with one of the standards. If the panel is somewhat
panel may be desirable to study one or another aspect of its
better than standard ( X) but not as good as standard (X+1) it
condition. Such procedure shall be confined to the minimum
is rated (X); if somewhat worse than standard (X) but not as bad
area absolutely necessary for the purpose, preferably not more
as standard ( X − 1) it is rated (X − 1). At the inspector’s option,
than 1 cm of a 10- by 15-cm panel.
decimal fractional ratings may be assigned.
6.3.1 If a large group of panels is being inspected at one
6. Assignment of Protection Rating
time, it is recommended that the panels be assessed individu-
6.1 The numerical rating system is
...