ASTM B578-87(1999)
(Test Method)Standard Test Method for Microhardness of Electroplated Coatings
Standard Test Method for Microhardness of Electroplated Coatings
SCOPE
1.1 This test method covers the determination of the hardness of metallic coatings upon various substrates. The measurements are made with the Knoop indenter under a test load of 0.245 N (25 gf) or 0.981 N (100 gf).
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Designation: B 578 – 87 (Reapproved 1999)
Standard Test Method for
Microhardness of Electroplated Coatings
This standard is issued under the fixed designation B 578; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3.1.3 Make the indentation near the center of the cross
section of the coating.
1.1 This test method covers the determination of the hard-
3.2 No single test load is applicable to all coatings. Use a
ness of metallic coatings upon various substrates. The mea-
load of 0.245 N for soft coatings (from 50 to 300 HK) and a
surements are made with the Knoop indenter under a test load
load of 0.981 N for hard coatings (greater than 300 HK).
of 0.245 N (25 gf) or 0.981 N (100 gf).
3.2.1 A load of less than 0.245 N is not recommended.
1.2 This standard does not purport to address all of the
However, when the length of the diagonal is great enough at a
safety concerns, if any, associated with its use. It is the
load of 0.245 N, which may occur for very soft coatings such
responsibility of the user of this standard to establish appro-
as tin and indium, a lighter load or a lower magnification shall
priate safety and health practices and determine the applica-
be specified provided the requirements of 3.3 are met. When
bility of regulatory limitations prior to use.
testing extremely hard coatings, a load greater than 0.981 N
2. Referenced Documents may be used provided this is specified in the purchase order.
The Knoop hardness number decreases appreciably with loads
2.1 ASTM Standards:
from 0.245 N to 0.981 N especially for the higher hardness
E 384 Test Method for Microhardness of Materials
numbers.
3. Special Requirements
3.3 Measure the length of the long diagonal to within 0.25
μm or 0.4 %, whichever is larger, at the magnification specified
3.1 In addition to the requirements listed herein, the test
in Test Method E 384.
method shall be performed in accordance with Test Method
3.4 When readings are taken in a direction parallel to the
E 384.
substrate, space them from each other by at least the length of
3.1.1 The measurement shall be made on the cross section
the long diagonal. When two readings are taken in the direction
with the long diagonal of the indentation parallel to the
of the short axis, separate them by at least the length of the
substrate using a Knoop indenter.
diagonal perpendicular to the substrate (short diagonal). In
NOTE 1—When a nondestructive test is necessary, the measurement
such cases, the distance from the substrate and from the outer
may be made normal to the surface provided that the whole of the
surface of the coating to an edge of the indentation shall be at
indentation is clearly delineated in the field of the microscope at the
least the width of the short diagonal.
magnification specified in Test Method E 384, and the coating thickness is
3.5 If the electroplated coating is cracked, or if cracks or
at least 0.7 that of the long diagonal. The outlines of the indentation must
be sharp and undistorted by any mechanical effects resulting from the “butterfly” markings (Test Method E 384, 7.2) appear when the
thinness of the coating such as “butterfly” fractures, etc. Values obtained
indentation load is applied or removed, the hardness measure-
from measurements made normal to the electroplated surface may not be
ment is invalid.
equivalent to those obtained on microsections and are not, therefore,
reportable according to Section 6.
4. Preparation of Test Specimen
3.1.2 The thickness of the coating shall be at least 38 μm for
4.1 Overplate the specimen to a thickness of at least 12 μm
soft coatings such as gold, copper, and silver, and 25 μm for
with a metal of a contrasting color whose hardness approxi-
hard coatings such as nickel, cobalt, iron, and hard gold. This
mates that of the coating.
is approximately equivalent to 0.6 times the length of the long
4.2 Cut out a section of the specimen approximately per-
Knoop diagonal.
pendicular to the electroplated coating.
4.3 Mount and polish the section as described in Test
Method E 384.
This test method is under the jurisdiction of ASTM Committee B-8 on Metallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.10 on
NOTE 2—Procedures 4.1 and 4.2 are interchangeable at the discretion of
General Test Methods.
the operator. A light etch following polishing may remove significant work
Current edition approved Jan. 30, 1987. Published March 1987. Originally
hardening.
published as B 578 – 73. Last
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