ASTM B320-60(2003)e1

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Endorsed by American
e1
Designation:B320–60 (Reapproved 2003) 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.
e NOTE—Section 2.1 was editorially updated in May 2003.
1. Scope 2.2 Purity of Water—Ordinary industrial or potable water
may be used for preparing solutions and rinsing.
1.1 This practice is intended to assist electroplaters in
establishing and maintaining a satisfactory pre-electroplating
3. Foundry Practices
cycle for malleable iron, gray iron, nodular iron, and white iron
3.1 The seacoal content of the molding and facing sands
castings.Itisalsointendedtoindicatecertainfoundrypractices
should be maintained at the maximum practicable limits to
whichwillfacilitatesubsequentfinishing.Mostofthepractices
minimize the occlusion of sand in the surfaces of the castings.
that follow have been based on experience with malleable and
3.2 Upon removal from the molds, castings should be
gray iron. However, since they are related to the other forms,
subjected to an abrading action (such as tumbling, grit blasting,
the same practices will probably apply. Nodular iron is also
or shot blasting) to remove as much as practicable of the
known as spheroidal or ductile iron, which is defined as cast
occluded molding sand. Residual sand and scale may be
iron with the graphite substantially in spherical shape and
removed, if necessary, by treatment in various proprietary
substantially free of flake graphite.
descaling baths. These are usually based on fused caustic soda,
1.2 This standard does not purport to address all of the
some of which use chemical oxidizing or reducing agents and
safety concerns, if any, associated with its use. It is the
others employ electrochemical action as well. This is particu-
responsibility of the user of this standard to establish appro-
larly important in the case of castings that will be annealed, to
priate safety and health practices and determine the applica-
prevent the burning on of sand during this operation. Castings
bility of regulatory limitations prior to use. Specific precau-
that will be warped or damaged by a blasting operation may be
tionary statements are given in 2.1.
pickled in a solution containing 200 to 250 mL/L of sulfuric
2. Reagents acid to remove occluded molding sand. See Warning state-
ment in 2.1.
2.1 Purity of Reagents—All acids and chemicals used in
3.3 Annealed castings should be given an additional abrad-
this practice are technical grade. Diluted acid solutions are
ing as described in 3.2 to remove any scale that may have been
based upon the following assay materials:
formed, as well as graphitic carbon that may be present at the
Hydrochloric acid (HCl): 31 mass %, density 1.16
surface.
g/mL
Hydrofluoric acid (HF): 47 mass %, density 1.186
g/mL
4. Nature of Cleaning
Sulfuric acid (H SO ): 93 mass %, density 1.83
2 4
4.1 The preparation of ferrous castings for electroplating
g/mL
involves the following basic steps in the order named:
(Warning—Use hydrofluoric acid with extreme care.)
4.1.1 The removal of oils, greases, residual polishing and
(Warning—Sulfuric acid should be slowly added to the
buffing compounds (if any), and shop dirt by cleaning,
approximate amount of water required with rapid mixing, and
4.1.2 The removal of oxide films and scales and the loos-
then after cooling, diluted to exact volume.)
ening of surface carbon by pickling or by salt bath treatment
(see 3.2),
4.1.3 The removal of smut caused by 4.1.2, and
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
4.1.4 Activation for electroplating.
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
4.2 Where excessive amounts of cutting oils used in ma-
Pre Treatment.
chining operations are present, it may be necessary to preclean
Current edition approved April 21, 2003. Published May 2003. Originally
approved in 1960. Last previous edition approved in 1997 as B 310 – 60 (1997). the parts before they reach the electroplating room. This may
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
e1
B320–60 (2003)
require the use of organic solvents, vapor degreasers, washing 6. Procedure for Racked Parts
machines of the power-spray type, emulsion cleaners, or
6.1 The following cycle may generally be used for racked
simple alkaline soak tanks. As short a time as possible should
parts which will subsequently be electroplated in still tanks,
elapse between this precleaning and the preplating cleaning
semiautomatic equipment, and full-automatic equipment:
cycle so as to prevent rusting of the parts. Where control of the
6.1.1 Precleaning—When castings have been subjected to
interval is not possible, parts should be left with a slightly
machining, polishing, buffing, or similar finishing processes, it
alkaline or very thin organic film.
is desirable and frequently essential that lubricants and finish-
ing compounds be removed by precleaning immediately fol-
5. Cleaning Solutions and Equipment
lowing such operations. This is especially important when the
5.1 The various solutions used for the treatment of mal-
lubricants contain unsaturated oils which, upon air oxidation,
leable and gray iron castings should be maintained by chemical
form films which are extremely difficult to remove. Preclean-
analysis so far as is practicable, such as determining the free
ing methods as listed in 4.2 may be employed.
acid and iron concentrations of the acid baths and using tests
6.2 Soak Cleaning—In the event precleaning of a heavily
recommended by the manufacturer, the effective components
soiled part is impossible or impracticable, soak cleaning to
of the proprietary cleaning solutions.
loosen oils and greases is recommended. The bath may be
5.2 All solutions should be discarded before they lose their
either an alkaline solution of such concentration as recom-
effectiveness, based on tests and experience.
mended by the supplier, and operated at a temperature as close
5.3 Whentheamountofsoilisexcessive,particularlywhere
to boiling as possible, or an emulsion-type cleaner operated as
no precleaning is done, it may be desirable to double the
specified by the supplier. In either case, agitation of the
cleaning and pickling facilities.Thus, while the first of any two
solution by air or solution pumping, or movement of the part,
particular solutions becomes heavily contaminated, the second
will prove beneficial. The time may be 5 min or more.
remains relatively clean and effective for further use.When the
6.3 Rinse—If the soak cleaner used is incompatible with the
first of a pair of solutions is discarded, it is replaced by the
subsequent cleaner, a rinse is indicated. The supplier will
second solution and a fresh second solution is prepared. This
normally suggest whether it is to be warm or cold, although a
system also reduces the possible carry-over of contaminants
warm rinse (60°C) is usually desirable following alkaline soak
such as oil and grease into subsequent solutions.
cleaning. In any case, agitation of the rinse water is desirable;
5.4 Where doubling the facilities is impossible or impracti-
and, in the case of cold-water rinses, a spray upon leaving the
cable, similar economies may be obtained to a degree by
tank is beneficial. The time of rinsing depends in part upon the
providing cleaner and pickle tanks with overflow dams, sumps
shape of the part, but should be no less than 10 s.
and pumps with which the solution may be recirculated. The
6.4 Anodic Cleaning—The part is made the anode in a
pump intake should be located approximately half-way down
solution of a properly compounded alkaline cleaner of a
the sump to preclude returning either settled-out solid dirt or
concentration recommended by the supplier. The cleaner
surface oil and grease to the processing tank. The outlet should
should be free-rinsing, and of high conductivity to permit a
be near the bottom of the processing tank at the end opposite
current density of 6 to 10A/dm at a tank potential of 6 to 9 V.
to the overflow dam so as to create some solution turbulence
The solution temperature should be from 90 to 100°C, and the
(for mechanical scrubbing benefits) and to ensure flow of
cleaning time from 1 to 2 min.
contaminated solution to the dam.
6.5 Rinse—The supplier of a proprietary cleaner will usu-
5.5 In electrified tanks removable electrodes should be
ally indicate whether his product rinses more freely in warm or
employed in preference to using the tank as an electrode, to
cold water. In general, rinsing should be done as described in
facilitate inspection and cleaning. To ensure good circuitry,
6.3, but preferably in a separate tank. Where practicable to do
positive contacts such as an inverted V hook for round bars
so, all rinses should be double rinses; that is, two separate
should be used. In alkaline cleaner tanks, where clean contact
rinses in succession, with the second cascading into the first for
is often a problem, submerged oversized steel tank rods are
water economy.
effective.
6.6 Acid Pickling—This stage of the cycle is the most
5.6 All immersion rinse tanks should be equipped with
dam-type overflows
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