ASTM B320-60(2008)

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Designation: B320 − 60(Reapproved 2008) Endorsed by American
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 B320; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Foundry Practices
1.1 This practice is intended to assist electroplaters in
3.1 The seacoal content of the molding and facing sands
establishing and maintaining a satisfactory pre-electroplating
should be maintained at the maximum practicable limits to
cycle for malleable iron, gray iron, nodular iron, and white iron
minimize the occlusion of sand in the surfaces of the castings.
castings.Itisalsointendedtoindicatecertainfoundrypractices
3.2 Upon removal from the molds, castings should be
which will facilitate subsequent finishing. Most of the practices
subjected to an abrading action (such as tumbling, grit blasting,
that follow have been based on experience with malleable and
or shot blasting) to remove as much as practicable of the
gray iron. However, since they are related to the other forms,
occluded molding sand. Residual sand and scale may be
the same practices will probably apply. Nodular iron is also
removed, if necessary, by treatment in various proprietary
known as spheroidal or ductile iron, which is defined as cast
descaling baths. These are usually based on fused caustic soda,
iron with the graphite substantially in spherical shape and
some of which use chemical oxidizing or reducing agents and
substantially free of flake graphite.
others employ electrochemical action as well. This is particu-
1.2 This standard does not purport to address all of the
larly important in the case of castings that will be annealed, to
safety concerns, if any, associated with its use. It is the
prevent the burning on of sand during this operation. Castings
responsibility of the user of this standard to establish appro-
that will be warped or damaged by a blasting operation may be
priate safety and health practices and determine the applica-
pickled in a solution containing 200 to 250 mL/L of sulfuric
bility of regulatory limitations prior to use. Specific precau-
acid to remove occluded molding sand. See Warning state-
tionary statements are given in 2.1.
ment in 2.1.
3.3 Annealed castings should be given an additional abrad-
2. Reagents
ing as described in 3.2 to remove any scale that may have been
2.1 PurityofReagents—All acids and chemicals used in this
formed, as well as graphitic carbon that may be present at the
practice are technical grade. Diluted acid solutions are based
surface.
upon the following assay materials:
Hydrochloric acid (HCl): 31 mass %, density 1.16
4. Nature of Cleaning
g/mL
Hydrofluoric acid (HF): 47 mass %, density 1.186
4.1 The preparation of ferrous castings for electroplating
g/mL
involves the following basic steps in the order named:
Sulfuric acid (H SO ): 93 mass %, density 1.83
2 4
4.1.1 The removal of oils, greases, residual polishing and
g/mL
buffing compounds (if any), and shop dirt by cleaning,
(Warning—Use hydrofluoric acid with extreme care.)
4.1.2 The removal of oxide films and scales and the loos-
(Warning—Sulfuric acid should be slowly added to the
ening of surface carbon by pickling or by salt bath treatment
approximate amount of water required with rapid mixing, and
(see 3.2),
then after cooling, diluted to exact volume.)
4.1.3 The removal of smut caused by 4.1.2, and
2.2 Purity of Water—Ordinary industrial or potable water
4.1.4 Activation for electroplating.
may be used for preparing solutions and rinsing.
4.2 Where excessive amounts of cutting oils used in ma-
chining operations are present, it may be necessary to preclean
the parts before they reach the electroplating room. This may
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
require the use of organic solvents, vapor degreasers, washing
Pre Treatment.
machines of the power-spray type, emulsion cleaners, or
Current edition approved Aug. 1, 2008. Published September 2008. Originally
e1
simple alkaline soak tanks. As short a time as possible should
approved in 1960. Last previous edition approved in 2003 as B310 – 60 (2003) .
DOI: 10.1520/B0320-60R08. elapse between this precleaning and the preplating cleaning
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B320 − 60 (2008)
cycle so as to prevent rusting of the parts. Where control of the 6. Procedure for Racked Parts
interval is not possible, parts should be left with a slightly
6.1 The following cycle may generally be used for racked
alkaline or very thin organic film.
parts which will subsequently be electroplated in still tanks,
semiautomatic equipment, and full-automatic equipment:
5. Cleaning Solutions and Equipment
6.1.1 Precleaning—When castings have been subjected to
machining, polishing, buffing, or similar finishing processes, it
5.1 The various solutions used for the treatment of mal-
leable and gray iron castings should be maintained by chemical is desirable and frequently essential that lubricants and finish-
ing compounds be removed by precleaning immediately fol-
analysis so far as is practicable, such as determining the free
acid and iron concentrations of the acid baths and using tests lowing such operations. This is especially important when the
lubricants contain unsaturated oils which, upon air oxidation,
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 Whentheamountofsoilisexcessive,particularlywhere
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
6.4 Anodic Cleaning—The part is made the anode in a
be near the bottom of the processing tank at the end opposite
solution of a properly compounded alkaline cleaner of a
to the overflow dam so as to create some solution turbulence
concentration recommended by the supplier. The cleaner
(for mechanical scrubbing benefits) and to ensure flow of
should be free-rinsing, and of high conductivity to permit a
contaminated solution to the dam.
current density of 6 to 10A/dm at a tank potential of 6 to 9 V.
5.5 In electrified tanks removable electrodes should be
The solution temperature should be from 90 to 100°C, and the
employed in preference to using the tank as an electrode, to
cleaning time from 1 to 2 min.
facilitate inspection and cleaning. To ensure good circuitry,
6.5 Rinse—Thesupplierofaproprietarycleanerwillusually
positive contacts such as an inverted V hook for round bars
indicatewhetherhisproductrinsesmorefreelyinwarmorcold
should be used. In alkaline cleaner tanks, where clean contact
water. In general, rinsing should be done as described in 6.3,
is often a problem, submerged oversized steel tank rods are
but preferably in a separate tank. Where practicable to do so,
effective.
all rinses should be double rinses; that is, two separate rinses in
5.6 All immersion rinse tanks should be equipped with
succession, with the second cascading into the first for water
dam-type overflows to ensure skimming of oil, grease, and
economy.
light dirt from the surface of the water. Water inlets should be
6.6 Acid Pickling—This stage of the
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