ASTM B320-60(1997)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued. NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information. Contact ASTM International (www.astm.org) for the latest information.
Endorsed by American
Designation: B 320 – 60 (Reapproved 1997) Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Practice for
Preparation of Iron Castings for Electroplating
This standard is issued under the fixed designation B 320; 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 3.2 Upon removal from the molds, castings should be
subjected to an abrading action (such as tumbling, grit blasting,
1.1 This practice is intended to assist electroplaters in
or shot blasting) to remove as much as practicable of the
establishing and maintaining a satisfactory pre-electroplating
occluded molding sand. Residual sand and scale may be
cycle for malleable iron, gray iron, nodular iron, and white iron
removed, if necessary, by treatment in various proprietary
castings. It is also intended to indicate certain foundry practices
descaling baths. These are usually based on fused caustic soda,
which will facilitate subsequent finishing. Most of the practices
some of which use chemical oxidizing or reducing agents and
that follow have been based on experience with malleable and
others employ electrochemical action as well. This is particu-
gray iron. However, since they are related to the other forms,
larly important in the case of castings that will be annealed, to
the same practices will probably apply. Nodular iron is also
prevent the burning on of sand during this operation. Castings
known as spheroidal or ductile iron, which is defined as cast
that will be warped or damaged by a blasting operation may be
iron with the graphite substantially in spherical shape and
pickled in a solution containing 200 to 250 mL/L of sulfuric
substantially free of flake graphite.
acid to remove occluded molding sand. See Caution in 2.1.
1.2 This standard does not purport to address all of the
3.3 Annealed castings should be given an additional abrad-
safety concerns, if any, associated with its use. It is the
ing as described in 3.2 to remove any scale that may have been
responsibility of the user of this standard to establish appro-
formed, as well as graphitic carbon that may be present at the
priate safety and health practices and determine the applica-
surface.
bility of regulatory limitations prior to use. Specific precau-
tionary statements are given in 2.1.
4. Nature of Cleaning
2. Reagents 4.1 The preparation of ferrous castings for electroplating
involves the following basic steps in the order named:
2.1 Purity of Reagents—All acids and chemicals used in
4.1.1 The removal of oils, greases, residual polishing and
this practice are technical grade. Diluted acid solutions are
buffing compounds (if any), and shop dirt by cleaning,
based upon the following assay materials:
4.1.2 The removal of oxide films and scales and the loos-
Hydrochloric acid (HCl): 31 mass %, density 1.16
ening of surface carbon by pickling or by salt bath treatment
g/mL
Hydrofluoric acid (HF): 47 mass %, density 1.186
(see 3.2),
g/mL
4.1.3 The removal of smut caused by 4.1.2, and
Caution—Use hydrofluoric acid with extreme care.
4.1.4 Activation for electroplating.
Sulfuric acid (H SO ): 93 mass %, density 1.83 g/mL 4.2 Where excessive amounts of cutting oils used in ma-
2 4
chining operations are present, it may be necessary to preclean
Caution—Sulfuric acid should be slowly added to the
the parts before they reach the electroplating room. This may
approximate amount of water required with rapid mixing, and
require the use of organic solvents, vapor degreasers, washing
then after cooling, diluted to exact volume.
machines of the power-spray type, emulsion cleaners, or
2.2 Purity of Water—Ordinary industrial or potable water
simple alkaline soak tanks. As short a time as possible should
may be used for preparing solutions and rinsing.
elapse between this precleaning and the preplating cleaning
cycle so as to prevent rusting of the parts. Where control of the
3. Foundry Practices
interval is not possible, parts should be left with a slightly
3.1 The seacoal content of the molding and facing sands
alkaline or very thin organic film.
should be maintained at the maximum practicable limits to
minimize the occlusion of sand in the surfaces of the castings.
5. Cleaning Solutions and Equipment
5.1 The various solutions used for the treatment of mal-
This practice is under the jurisdiction of ASTM Committee B-8 on Metallic and
leable and gray iron castings should be maintained by chemical
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
analysis so far as is practicable, such as determining the free
Substrate Preparation.
acid and iron concentrations of the acid baths and using tests
Current edition effective Sept. 19, 1960. Originally issued 1957. Replaces
B320–57 T.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued. NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information. Contact ASTM International (www.astm.org) for the latest information.
B 320 – 60 (1997)
recommended by the manufacturer, the effective components form films which are extremely difficult to remove. Preclean-
of the proprietary cleaning solutions. ing methods as listed in 4.2 may be employed.
5.2 All solutions should be discarded before they lose their
6.2 Soak Cleaning—In the event precleaning of a heavily
effectiveness, based on tests and experience.
soiled part is impossible or impracticable, soak cleaning to
5.3 When the amount of soil is excessive, particularly where
loosen oils and greases is recommended. The bath may be
no precleaning is done, it may be desirable to double the
either an alkaline solution of such concentration as recom-
cleaning and pickling facilities. Thus, while the first of any two
mended by the supplier, and operated at a temperature as close
particular solutions becomes heavily contaminated, the second
to boiling as possible, or an emulsion-type cleaner operated as
remains relatively clean and effective for further use. When the
specified by the supplier. In either case, agitation of the
first of a pair of solutions is discarded, it is replaced by the
solution by air or solution pumping, or movement of the part,
second solution and a fresh second solution is prepared. This
will prove beneficial. The time may be 5 min or more.
system also reduces the possible carry-over of contaminants
6.3 Rinse—If the soak cleaner used is incompatible with the
such as oil and grease into subsequent solutions.
subsequent cleaner, a rinse is indicated. The supplier will
5.4 Where doubling the facilities is impossible or impracti-
normally suggest whether it is to be warm or cold, although a
cable, similar economies may be obtained to a degree by
warm rinse (60°C) is usually desirable following alkaline soak
providing cleaner and pickle tanks with overflow dams, sumps
cleaning. In any case, agitation of the rinse water is desirable;
and pumps with which the solution may be recirculated. The
and, in the case of cold-water rinses, a spray upon leaving the
pump intake should be located approximately half-way down
tank is beneficial. The time of rinsing depends in part upon the
the sump to preclude returning either settled-out solid dirt or
shape of the part, but should be no less than 10 s.
surface oil and grease to the processing tank. The outlet should
be near the bottom of the processing tank at the end opposite 6.4 Anodic Cleaning—The part is made the anode in a
to the overflow dam so as to create some solution turbulence solution of a properly compounded alkaline cleaner of a
(for mechanical scrubbing benefits) and to ensure flow of concentration recommended by the supplier. The cleaner
contaminated solution to the dam.
should be free-rinsing, and of high conductivity to permit a
5.5 In electrified tanks removable electrodes should be current density of 6 to 10 A/dm at a tank potential of 6 to 9 V.
employed in preference to using the tank as an electrode, to
The solution temperature should be from 90 to 100°C, and the
facilitate inspection and cleaning. To ensure good circuitry,
cleaning time from 1 to 2 min.
positive contacts such as an inverted V hook for round bars
6.5 Rinse—The supplier of a proprietary cleaner will usu-
should be used. In alkaline cleaner tanks, where clean contact
ally indicate whether his product rinses more freely in warm or
is often a problem, submerged oversized steel tank rods are
cold water. In general, rinsing should be done as described in
effective.
6.3, but preferably in a separate tank. Where practicable to do
5.6 All immersion rinse tanks should be equipped with
so, all rinses should be double rinses; that is, two separate
dam-type overflows to ensure skimming of oil, grease, and
rinses in succession, with the second cascading into the first for
light dirt from the surface of the water. Water inlets should be
water economy.
at the bottom of the tank, and should be of a size sufficient to
6.6 Acid Pickling—This stage of the cycle is the most
provide an adequate flow of water. It is desirable that sub-
critical, and its operating conditions are dependent on the type
merged inlet pipes be equipped with syphon-breakers (as
of electroplating to follow. Most of the difficulties in electro-
required by law in many areas) not only to prevent the
plating of gray iron and malleable iron castings are caused by
backflow of contaminated water into the mains, but also to
the free graphitic carbon, flake or nodular, which is present at
produce a beneficial turbulence or scrubbing action due to the
the surface of the part. I
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