ASTM B480-88(1995)

Standard Guide for Preparation of Magnesium and Magnesium Alloys for Electroplating

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.
1.2 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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 precautionary statements, see 5.1.1 and 5.2.9.2.

General Information

• Status: Historical
• Publication Date: 24-Mar-1988
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.02 - Pre Treatment

Relations

• Replaced By: ASTM B480-88(2001) - Standard Guide for Preparation of Magnesium and Magnesium Alloys for Electroplating
• Effective Date: 25-Mar-1988
• Referred By: ASTM B905-00(2021) - Standard Test Methods for Assessing the Adhesion of Metallic and Inorganic Coatings by the Mechanized Tape Test
• Effective Date: 25-Mar-1988
• Referred By: ASTM B689-97(2023) - Standard Specification for Electroplated Engineering Nickel Coatings
• Effective Date: 25-Mar-1988

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 480 – 88 (Reapproved 1995)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Guide for
Preparation of Magnesium and Magnesium Alloys for
Electroplating
This standard is issued under the fixed designation B 480; 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 5. Processes
1.1 This guide describes two processes used for plating on 5.1 Procedures:
magnesium and magnesium alloys: direct electroless nickel 5.1.1 Wheel polish and buff parts for smooth, highly pol-
plating and zinc immersion. Some users report that the direct ished surfaces. Tumble and burnish small parts. Acid pickle the
electroless nickel procedure does not produce quite as high a parts after use of wire brushing or steel wool.
level of adhesion as zinc immersion.
NOTE 1—Caution: Because of the high flammability of powdered
1.2 This standard does not purport to address all of the
magnesium, special precautions against fire are important. Polishing and
safety concerns, if any, associated with its use. It is the
buffing lathes should be kept scrupulously clean. Dust from grinding in
responsibility of the user of this standard to establish appro- and around lathes should be swept up and placed in closed containers for
proper disposal. Exhaust systems should be cleaned frequently and the
priate safety and health practices and determine the applica-
residues handled similarly. If abrasives are used in tumble finishing,
bility of regulatory limitations prior to use. For specific hazard
similar precautionary techniques should be used for the solids from the
statements, see Notes 1 and 7.
abrasive slurry.
2. Referenced Documents
5.1.2 Chemical—Remove oil and grease in an alkaline soak
cleaner. Remove other soils and coatings in suitable acid
2.1 ASTM Standards:
pickling solutions.
B 322 Practice for Cleaning Metals Prior to Electroplating
NOTE 2—General information on the cleaning of metals is given in
3. Significance and Use
Practice B 322.
3.1 Metals are electroplated on magnesium for various
5.2 General Electroplating Procedure:
purposes: solderability, RF grounding, hermetic sealing, wear
5.2.1 Remove oil, grease, and other soils left from preplat-
resistance, corrosion resistance, appearance, and electrical
ing procedures by soak cleaning in an alkaline cleaner suitable
conductivity, for example. Because magnesium is covered with
for magnesium.
a naturally occurring oxide film, usual procedures for the
5.2.2 Rinse in cold water.
preparation of metals for autocatalytic or electrolytic plating
NOTE 3—As generally used in rinsing terminology, cold water refers to
cannot be used.
water from an unheated water supply as opposed to heated water used for
4. Reagents drying or other purposes. In some areas, particularly in water, ambient
water temperatures may be too low for effective rinsing. In those
4.1 Purity of Reagents—All acids and chemicals used in
instances, the rinse water may need to be heated. A minimum temperature
this guide are of technical grade. Acid and base solutions are
of 16°C is recommended for effective rinsing.
based on the following assay materials:
5.2.3 Electroclean parts in an alkaline electrocleaner suit-
Ammonium hydroxide (NH OH) 30 mass %, density 0.895 g/L
able for magnesium. Make the magnesium cathodic at 7.5 to 13
Nitric acid (HNO ) 67 mass %, density 1.16 g/L
Sulfuric acid (H SO ) 93 mass %, density 1.40 g/L
A/dm and 85°C.
2 4
Hydrofluoric acid (HF) 70 mass %, density 1.258 g/L
5.2.4 Rinse in cold water.
Phosphoric acid (H PO ) 85 mass %, density 1.689 g/L
3 4
5.2.5 Pickle in one of the following solutions:
4.2 Purity of Water—All water used for solutions, whether
5.2.5.1 Ferric Nitrate Pickle:
new or recycled, should be monitored for cations, anions, and
Chromic acid (CrO ) 180 g/L
organic matter that are known to interfere with the plating Ferric nitrate (Fe(NO )·9H O) 40 g/L
3 2
Potassium fluoride (KF) 3.5 g/L
process.
Temperature 16 to 38°C
Time 15 s to 3 min
This practice is under the jurisdiction of ASTM Committee B-8 on Metallic and
NOTE 4—This pickle removes metal from a surface at the rate of 3
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
μm/min at 38°C. Where no dimensional change can be tolerated, use of the
Substrate Preparation.
Current edition approved March 25, 1988. Published May 1988. Originally
e
published as B 480 – 68. Last previous edition B 480 – 68 (1980) .
2 3
Annual Book of ASTM Standards, Vol 02.05. Magnesium Finishing, The Dow Metal Products Co., Midland, MI.
B 480
chromic acid pickle in 5.2.5.2 is recommended.
5.2.11 Copper strike in either of the following:
3 Bath 1:
5.2.5.2 Chromic Acid Pickle:
Chromic acid (CrO ) 180 g/L
Copper cyanide (CuCN) 38 to 42 g/L
Temperature 16 to 93°C
Potassium cyanide (KCN) 64.5 to 71.5 g/L
Time 2 to 10 min Potassium fluoride (KF) 28.5 to 31.5 g/L
Free potassium cyanide 7 to 8 g/L
NOTE 5—The use of chromic acid pickles may leave chromate films on pH 9.6 to 10.4
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
Sodium cyanide (NaCN) 50 to 55 g/L
5.2.7 Activate in the following solution:
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 15 s to 2 min
5.2.11.1 Plate the parts about 6 min. Cathode rod agitation is
5.2.8 Rinse in cold water.
suggested. With either bath make electrical contact quickly
5.2.9 Zinc coat in the following solution:
with initial current 5 to 10 A/dm , then lower current to 1 to 2.5
Zinc sulfate (ZnSO ·H O) 30 g/L A/dm .
4 2
Tetrasodium pyrophosphate (Na P O ) 120 g/L
4 2 7
5.2.12 Rinse thoroughly in cold water.
Sodium fluoride (NaF) or 5 g/L or
5.2.13 Dip in diluted acid (1 % by vol sulfuric acid + 99 %
Lithium fluoride (LiF) 2 g/L
Sodium carbonate (Na CO ) 5 g/L by vol water).
2 3
5.2.14 Rinse in cold water.
5.2.9.1 Because of the low solubility of the tetrasodium
5.2.15 Apply subsequent electrodeposits or autocatalytic
pyrophosphate, it is generally necessary to mix this solution in
nickel in accordance with standard commercial electroplating
an elevated temperature from 70 to 85°C. It is also advanta-
practice. Use plastisol-coated racks that are fitted with stain-
geous to alternately add portions of the zinc sulfate and
less steel or phosphor-bronze rack tips.
pyrophosphate. When these ingredients are completely dis-
5.3 Autocatalytic Nickel Plating Magnesium:
solved, add and dissolve the balance of the ingredients in the
5.3.1 Surface Conditioning—See 5.1.1 and 5.1.2, and 5.2.1-
order given.
5.2.4.
5.3.2 Pickling—Pickle in (1) chromic acid as directed in
NOTE 6—Either sodium fluori
...