ASTM B480-88(2006)
(Guide)Standard Guide for Preparation of Magnesium and Magnesium Alloys for Electroplating
Standard Guide for Preparation of Magnesium and Magnesium Alloys for Electroplating
SIGNIFICANCE AND USE
Metals are electroplated on magnesium for various purposes: solderability, RF grounding, hermetic sealing, wear resistance, corrosion resistance, appearance, and electrical conductivity, for example. Because magnesium is covered with a naturally occurring oxide film, usual procedures for the preparation of metals for autocatalytic or electrolytic plating cannot be used.
SCOPE
1.1 This guide describes two processes used for plating on magnesium and magnesium alloys: direct electroless nickel plating and zinc immersion. Some users report that the direct electroless nickel procedure does not produce quite as high a level of adhesion as zinc immersion.
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. For specific hazard statements, see .
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Standards Content (Sample)
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Designation:B480–88(Reapproved 2006)
Standard Guide for
Preparation of Magnesium and Magnesium Alloys for
Electroplating
This standard is issued under the fixed designation B480; 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
Hydrofluoric acid (HF) 70 mass %, density 1.258 g/L
Phosphoric acid (H PO ) 85 mass %, density 1.689 g/L
3 4
1.1 This guide describes two processes used for plating on
4.2 Purity of Water—All water used for solutions, whether
magnesium and magnesium alloys: direct electroless nickel
plating and zinc immersion. Some users report that the direct new or recycled, should be monitored for cations, anions, and
organic matter that are known to interfere with the plating
electroless nickel procedure does not produce quite as high a
level of adhesion as zinc immersion. process.
1.2 This standard does not purport to address all of the
5. Processes
safety concerns, if any, associated with its use. It is the
5.1 Procedures:
responsibility of the user of this standard to establish appro-
5.1.1 Wheel polish and buff parts for smooth, highly pol-
priate safety and health practices and determine the applica-
ished surfaces.Tumble and burnish small parts.Acid pickle the
bility of regulatory limitations prior to use. For specific hazard
parts after use of wire brushing or steel wool. (Warning—
statements, see 5.1.1 and 5.2.9.2.
Because of the high flammability of powdered magnesium,
2. Referenced Documents
special precautions against fire are important. Polishing and
buffing lathes should be kept scrupulously clean. Dust from
2.1 ASTM Standards:
grinding in and around lathes should be swept up and placed in
B322 Guide for Cleaning Metals Prior to Electroplating
closed containers for proper disposal. Exhaust systems should
3. Significance and Use
be cleaned frequently and the residues handled similarly. If
abrasives are used in tumble finishing, similar precautionary
3.1 Metals are electroplated on magnesium for various
purposes: solderability, RF grounding, hermetic sealing, wear techniques should be used for the solids from the abrasive
resistance, corrosion resistance, appearance, and electrical slurry.)
conductivity,forexample.Becausemagnesiumiscoveredwith 5.1.2 Chemical—Remove oil and grease in an alkaline soak
a naturally occurring oxide film, usual procedures for the cleaner. Remove other soils and coatings in suitable acid
preparation of metals for autocatalytic or electrolytic plating pickling solutions.
cannot be used.
NOTE 1—General information on the cleaning of metals is given in
Practice B322.
4. Reagents
5.2 General Electroplating Procedure:
4.1 Purity of Reagents—All acids and chemicals used in
5.2.1 Remove oil, grease, and other soils left from preplat-
this guide are of technical grade. Acid and base solutions are
ing procedures by soak cleaning in an alkaline cleaner suitable
based on the following assay materials:
for magnesium.
Ammonium hydroxide (NH OH) 30 mass %, density 0.895 g/L
5.2.2 Rinse in cold water.
Nitric acid (HNO ) 67 mass %, density 1.16 g/L
Sulfuric acid (H SO ) 93 mass %, density 1.40 g/L
2 4
NOTE 2—As generally used in rinsing terminology, cold water refers to
water from an unheated water supply as opposed to heated water used for
drying or other purposes. In some areas, particularly in water, ambient
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and water temperatures may be too low for effective rinsing. In those
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
instances, the rinse water may need to be heated.Aminimum temperature
Treatment.
of 16°C is recommended for effective rinsing.
Current edition approved April 1, 2006. Published April 2006. Originally
5.2.3 Electroclean parts in an alkaline electrocleaner suit-
approved in 1968. Last previous edition approved in 2001 as B480 – 88 (2001).
DOI: 10.1520/B0480-88R06.
ableformagnesium.Makethemagnesiumcathodicat7.5to13
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 2
A/dm and 85°C.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.2.4 Rinse in cold water.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 5.2.5 Pickle in one of the following solutions:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B480–88 (2006)
5.2.5.1 Ferric Nitrate Pickle: 5.2.10 Rinse thoroughly in cold water.
Chromic acid (CrO ) 180 g/L
NOTE 6—For alloys M1660, M13120, M13312, or M13310, a double
Ferric nitrate (Fe(NO )·9H O) 40 g/L
3 2
zinc immersion is required. After step 5.2.10, steps 5.2.7-5.2.10 are
Potassium fluoride (KF) 3.5 g/L
repeated followed by step 5.2.11. It is advisable to use separate solutions
Temperature 16 to 38°C
Time 15sto3min for steps 5.2.7 and 5.2.9 when the double zinc immersion technique is
practiced.
NOTE 3—This pickle removes metal from a surface at the rate of 3
µm/minat38°C.Wherenodimensionalchangecanbetolerated,useofthe
5.2.11 Copper strike in either of the following:
chromic acid pickle in 5.2.5.2 is recommended.
Bath 1:
5.2.5.2 Chromic Acid Pickle:
Copper cyanide (CuCN) 38 to 42 g/L
Chromic acid (CrO ) 180 g/L
Potassium cyanide (KCN) 64.5 to 71.5 g/L
Temperature 16 to 93°C
Potassium fluoride (KF) 28.5 to 31.5 g/L
Time 2to10min
Free potassium cyanide 7 to 8 g/L
pH 9.6 to 10.4
NOTE 4—The use of chromic acid pickles may leave chromate films on
Temperature 54 to 60°C
the surface that will reduce the adhesion of the subsequently deposited
coating.
Bath 2:
5.2.6 Rinse in cold water.
Copper cyanide (CuCN) 38 to 42 g/L
5.2.7 Activate in the following solution:
Sodium cyanide (NaCN) 50 to 55 g/L
Rochelle salt (KNaC H O ·4H O) 40 to 48 g/L
4 4 6 2
Phosphoric acid, (H PO ) 20 % by vol
3 4
Free sodium cyanide 7 to 8 g/L
Ammonium bifluoride (NH HF ) 105 g/L
4 2
pH 9.6 to 10.4
Temperature 16 to 38°C
Temperature 54 to 60°C
Time 15sto2min
5.2.11.1 Platethepartsabout6min.Cathoderodagitationis
5.2.8 Rinse in cold water.
suggested. With either bath make electrical contact quickly
5.2.9 Zinc coat in the following solution:
withinitialcurrent5to10A/dm ,thenlowercurrentto1to2.5
Zinc sulfate (ZnSO ·H O) 30 g/L
4 2
Tetrasodium pyrophosphate (Na P O ) 120 g/L A/dm .
4 2 7
Sodium fluoride (NaF) or 5 g/L or
5.2.12 Rinse thoroughly in cold water.
Lithium fluoride (LiF) 2 g/L
5.2.13 Dip in diluted acid (1 % by vol sulfuric acid + 99 %
Sodium carbonate (Na CO)5g/L
2 3
by vol water).
5.2.9.1 Because of the low solubility of the tetrasodium
5.2.14 Rinse in cold water.
pyrophosphate, it is generally necessary to mix this solution in
5.2.15 Apply subsequent electrodeposits or autocatalytic
an elevated temperature from 70 to 85°C. It is also advanta-
nickel in accordance with standard commercial electroplating
geous to alternately add portions of the zinc sulfate and
practice. Use plastisol-coated racks that are fitted with stain-
pyrophosphate. When these ingredients are completely dis-
less steel or phosphor-bronze rack tips.
solved, add and dissolve the balance of the ingredients in the
5.3 Autocatalytic Nickel Plating Magnesium:
ord
...
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