ASTM B507-86(2008)e1
(Practice)Standard Practice for Design of Articles to Be Electroplated on Racks
Standard Practice for Design of Articles to Be Electroplated on Racks
SIGNIFICANCE AND USE
When an article is to be electroplated, it is necessary to consider not only the characteristics of the electroplating process, but also the design of the part to minimize electroplating and finishing costs and solution dragout as well as to improve appearance and functionality. It is often possible during the design and engineering stages to make small adjustments in shape that will result in considerable benefit toward a better quality part at a lower cost.
The specific property of an electroplating process that would require some attention to the details of optional designs, is the throwing power of the electroplating solution. Throwing power is the improvement of the coating distribution over the primary current distribution on an electrode (usually cathode) in a given solution, under specified conditions.
SCOPE
1.1 This practice covers design information for parts to be electroplated on racks. The recommendations contained herein are not mandatory, but are intended to give guidance toward good practice.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:B507 −86(Reapproved2008)
StandardPractice for
Design of Articles to Be Electroplated on Racks
This standard is issued under the fixed designation B507; 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.
´ NOTE—The units statement in subsection 1.2 was corrected editorially in April 2008.
1. Scope plates have a nonuniform distribution of current when freely
suspended in a bath as shown in Fig. 1. In this example, the
1.1 This practice covers design information for parts to be
current lines tend to concentrate as corners, and edges (high-
electroplated on racks. The recommendations contained herein
current density) of the part. Consequently more metal is
are not mandatory, but are intended to give guidance toward
deposited at the high-current density areas than at the low-
good practice.
current density areas.
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4. Relative Throwing Powers of Different Electrolytes
standard.
4.1 Throwing power is not the same for all metals and all
1.3 This standard does not purport to address all of the
electroplating baths. Table 1 lists the commonly used electro-
safety concerns, if any, associated with its use. It is the
plating processes. They are arranged according to decreasing
responsibility of the user of this standard to establish appro-
throwing power.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4.2 A Rochelle-type copper electroplating solution has ex-
cellent throwing power compared to the poor throwing power
2. Significance and Use
of a chromic acid solution used to deposit chromium. The
2.1 When an article is to be electroplated, it is necessary to
widely used Watts-type nickel bath has fair throwing power.
consider not only the characteristics of the electroplating
process, but also the design of the part to minimize electro-
5. Geometric Factors Determining Deposit Distribution
plating and finishing costs and solution dragout as well as to
improve appearance and functionality. It is often possible
5.1 Since a metal deposits preferentially at protuberances,
during the design and engineering stages to make small
such as sharp corners, edges, fins, and ribs, these should be
adjustments in shape that will result in considerable benefit
rounded to a radius of at least 0.4 and preferably 0.8 mm to
toward a better quality part at a lower cost.
avoid excessive buildup. Contouring a base corner in a
depression is also recommended to avoid thickness deficiency
2.2 The specific property of an electroplating process that
at the location.
would require some attention to the details of optional designs,
is the throwing power of the electroplating solution. Throwing
5.2 The width-to-depth ratio of a depression or recess
power is the improvement of the coating distribution over the
should be held to more than three as shown in Fig. 2.
primary current distribution on an electrode (usually cathode)
Otherwise, a special auxiliary anode must be employed inside
in a given solution, under specified conditions.
the recess to promote more uniform current distribution. An
auxiliary anode is usually made of the depositing metal and is
3. Current Distribution and Throwing Power
placed close to the low-current density areas to enhance metal
3.1 The apparent current during practical electroplating is
deposition at those regions.
never uniform over the surface of the product. Even parallel
5.3 All sharp edges and base angles of a recess should be
rounded to a radius of 0.25 times or more the depth of the
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.01 on
recess as shown in Fig. 3. When sharp recess angles are
Ancillary Activities.
required for a functional purpose, the electroplater cannot be
Current edition approved April 1, 2008. Published April 2008. Originally
expected to meet a minimum thickness at those locations
approved in 1970. Last previous edition approved in 2003 as B507 – 86 (2003).
DOI: 10.1520/B0507-86R08E01. unless it is specifically required.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B507−86(Reapproved2008)
FIG. 1 Current Density Distribution and Typical Electrodeposit (filled area)
TABLE 1 Relative Throwing Powers of Common Electroplating
erence to the figures enables similar conclusions to be drawn
Baths
with most other metals, excluding chromium. The ranges will
Bath/Metal Ranking
be smaller for metals above nickel in Table 1 and larger for
Rochell copper (cyanide based) Excellent
metals below nickel.
Cyanide cadmium Excellent
6.2 Improvement in nickel distribution can be gained inside
Cyanide gold Good
Cyanide silver Good
an angle by increasing the angle size, as shown in Fig. 4.Two
Alkaline tin Good
surfaces meeting at an angle of 60° show an average-to-
Cyanide zinc Good
Alkaline non cyanide zinc Good minimumthicknessratioof3.3,andincreasingtheangleto90°
Fluoborate lead Good
or 120° the ratio can be reduced to 2.7 or 1.9, respectively.
All chloride nickel Fair
Tin nickel Fair 6.3 Sharp corners should be given as large a radius as
Sulfamate nickel Fair
practical to improve metal distribution in a recess and avoid
A
Watts nickel Fair
excessive buildup on protuberances. Fig. 6(a) illustrates a part
Bright nickel F
...
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