ASTM B764-04(2021)
(Test Method)Standard Test Method for Simultaneous Thickness and Electrode Potential Determination of Individual Layers in Multilayer Nickel Deposit (STEP Test)
Standard Test Method for Simultaneous Thickness and Electrode Potential Determination of Individual Layers in Multilayer Nickel Deposit (STEP Test)
SIGNIFICANCE AND USE
4.1 The ability of a multilayer nickel deposit to enhance corrosion resistance is a function of the difference in the electrode potentials of the nickel layers (as measured individually at a fixed current density in a given electrolyte versus a reference electrode) and the thicknesses of the layers. The potential differences must be sufficient to cause the bright nickel or top layer to corrode preferentially and sacrificially with respect to the semi-bright nickel layer beneath it.
4.2 This test procedure allows the measurement of these potential differences directly on an electroplated part rather than on separate foil specimens in such a way that time determines the thickness of each layer, while the potential difference between nickel layers is an indication of the corrosion resistance of the total nickel deposit.
4.3 The interpretation and evaluation of the results of this test should be by agreement between the purchaser and the manufacturer.
Note 1: This test may be used as a quality assurance test of the multilayer nickel coatings applied in production. It should be understood that due to many factors that influence the progress of corrosion during actual use of the part, the performance of different multilayer nickel deposits in the test cannot be taken as an absolute indicator of the relative corrosion resistance of these deposits in service.
SCOPE
1.1 This test method closely estimates the thickness of individual layers of a multilayer nickel electrodeposit and the potential differences between the individual layers while being anodically stripped at constant current density.2,3
1.2 This test method does not cover deposit systems other than multilayer electroplated nickel deposits.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B764 − 04 (Reapproved 2021)
Standard Test Method for
Simultaneous Thickness and Electrode Potential
Determination of Individual Layers in Multilayer Nickel
1
Deposit (STEP Test)
This standard is issued under the fixed designation B764; 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 3. Summary of Test Method
1.1 This test method closely estimates the thickness of
3.1 This procedure is a modification of the well-known
individual layers of a multilayer nickel electrodeposit and the
coulometric method of thickness testing (Test Method B504).
potential differences between the individual layers while being
It is also known as the anodic dissolution or electrochemical
2,3
anodically stripped at constant current density.
stripping method.
1.2 This test method does not cover deposit systems other
3.2 Coulometric thickness testing instruments are based on
than multilayer electroplated nickel deposits.
the anodic dissolution (stripping) of the deposit at constant
1.3 This standard does not purport to address all of the
current, while the time is measured to determine thickness.As
safety concerns, if any, associated with its use. It is the commonly practiced, the method employs a small cell that is
responsibility of the user of this standard to establish appro-
filled with an appropriate electrolyte, and the test specimen
priate safety, health, and environmental practices and deter- serves as the bottom of the cell. To the bottom of the cell is
mine the applicability of regulatory limitations prior to use.
attached a rubber or plastic gasket whose opening defines the
1.4 This international standard was developed in accor- measuring(stripping,anodic)area.Ifametalliccellisused,the
dance with internationally recognized principles on standard-
rubber gasket also electrically insulates the test specimen from
ization established in the Decision on Principles for the the cell.With the specimen as the anode and the cell or agitator
Development of International Standards, Guides and Recom-
tube as the cathode, a constant direct current is passed through
mendations issued by the World Trade Organization Technical the cell until the nickel layer is dissolved. A sudden change in
Barriers to Trade (TBT) Committee.
voltagebetweentheelectrodesoccurswhenadifferentmetallic
layer starts to dissolve.
2. Referenced Documents
3.3 Each different metal or species of the same metal
4
2.1 ASTM Standards:
requires a given voltage to keep the current constant while
B456 Specification for Electrodeposited Coatings of Copper
being stripped. As one nickel layer is dissolved away and the
Plus Nickel Plus Chromium and Nickel Plus Chromium
next layer becomes exposed, there will be a voltage change
B504 Test Method for Measurement of Thickness of Metal-
(assuming a constant current and difference in the electro-
lic Coatings by the Coulometric Method
chemical characteristics of the two nickel layers). The elapsed
D1193 Specification for Reagent Water
timeatwhichthisvoltagechangeoccurs(relativetothestartof
the test or previous voltage change) is a measure of the deposit
thickness.
1
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
3.4 At the same time, the amplitude of the voltage change
Test Methods.
canbeobserved.Thatis,theease(ordifficulty)withwhichone
Current edition approved April 1, 2021. Published May 2021. Originally
approved in 1986. Last previous edition approved in 2014 as B764 – 04(2014) .
layer can be dissolved or stripped with reference to another
DOI: 10.1520/B0764-04R21.
layer can be compared. The lower the voltage needed the more
2
For discussion of this test, see Harbulak, E. P., “Simultaneous Thickness and
active the metal or the greater the tendency to corrode
Electrochemical Potential Determination of Individual Layers in Multilayer Nickel
Deposits,” Plating and Surface Finishing, Vol 67, No. 2, February 1980, pp. 49–54. preferentially to a more noble metal adjacent to it.
3
3.5 Where the metallic layers are of such a similar nature
U.S. Patent 4,310,389. Assignee: The Chrysler Corp., Highland Park, MI
48203.
that change of the stripping voltage is small, there can be
4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
problems in detecting this change if the voltage between the
contact ASTM Customer Service at service@astm.org. For A
...
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