ASTM B975-22

Standard Test Method for Measurement of Internal Stress of Metallic Coatings by Split Strip Evaluation (Deposit Stress Analyzer Method)

SIGNIFICANCE AND USE
5.1 Internal stress in applied coatings exhibits potential to cause a breakdown of resistance to corrosion and erosion as a result of the formation of fractures from micro-cracking and macro-cracking within the applied coating. This phenomenon can also cause blistering, peeling, reduction of fatigue strength, and loss. The resulting stress can be tensile in nature, causing the deposit to contract, or compressive in nature, causing the deposit to expand.  
5.2 To maintain quality assurance by the bent strip method, it is necessary to monitor production processes for acceptable levels of internal deposit stress in applied coatings. Most low values are false. Initial values tend to be lower than the actual value because of the effect of stock material edge burrs and the resistance of the stock material to bending. Excessive deposit thickness causes lower-than-true value since the coating overpowers and changes the initial modulus of elasticity of the test piece, which becomes more difficult to bend as the coating continues to build upon it. This phenomenon can be corrected considerably by use of a formula that compensates for modulus of elasticity differences between the deposit and the substrate materials, but it does remain a factor. See Eq 3.
Note 1: The highest value of the internal deposit stress as obtained on a stress-versus-plating-thickness curve is usually the truest value of the internal deposit stress.
SCOPE
1.1 This test method for determining the internal tensile or compressive stress in applied coatings is quantitative. It is applicable to metallic layers that are applied by the processes of electroplating or chemical deposition that exhibit internal tensile or compressive stress values from 200 psi to 145 000 psi (1.38 MPa to 1000 MPa).  
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other. Conversion between unit systems may result in errors that can cause confusion and should be avoided.  
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

• Status: Published
• Publication Date: 31-Oct-2022
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.10 - Test Methods

Relations

• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM B636-84(2010) - Standard Test Method for Measurement of Internal Stress of Plated Metallic Coatings with the Spiral Contractometer
• Effective Date: 01-Nov-2010
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E177-08 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2008
• Refers: ASTM E177-06b - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 15-Nov-2006
• Refers: ASTM E177-06a - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2006
• Refers: ASTM B636-84(2006)e1 - Standard Test Method for Measurement of Internal Stress of Plated Metallic Coatings with the Spiral Contractometer
• Effective Date: 01-Apr-2006
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM E177-06 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004
• Refers: ASTM E177-04 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004
• Refers: ASTM E177-04e1 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004

Overview

ASTM B975-22 specifies the standard test method for determining the internal tensile or compressive stress of metallic coatings using the split strip evaluation, commonly known as the Deposit Stress Analyzer Method. This quantitative method is essential for assessing the deposited stress levels in electroplated or chemically deposited metallic layers. Proper stress measurement is critical because excessive internal stresses can cause coatings to crack, blister, or lose adhesion, significantly affecting corrosion resistance and mechanical performance.

The method is widely used in manufacturing quality control to ensure that coatings applied to metal substrates remain durable and perform as intended in service environments.

Key Topics

• Internal Stress in Metallic Coatings: Internal stress can be either tensile (causing contraction) or compressive (causing expansion) and directly impacts the durability and effectiveness of metallic coatings.
• Deposit Stress Analyzer Method: Utilizes a split test strip, calibrated by the manufacturer, to rapidly and economically measure internal stress. After plating, the deflection between the test strip legs is measured and converted into a stress value using specific formulas.
• Measurement Range: Applicable to stress values from 200 psi to 145,000 psi (1.38 MPa to 1000 MPa), covering a wide range of common electroplated or chemically deposited metals.
• Quality Assurance: Ensures production processes maintain acceptable stress levels, preventing defects like micro-cracking, blistering, peeling, and reduction in fatigue strength.
• Units: Both SI and inch-pound units are standardized; conversion between the two should be carefully managed to avoid errors.

Applications

The test method described in ASTM B975-22 offers practical value in several key industries and operational scenarios:

• Electroplating and Chemical Deposition: Used by manufacturers and plating companies to verify that applied metal coatings will not fail due to excessive internal stress.
• Quality Control Laboratories: An efficient tool for routine inspection of coating baths, providing quick and reliable stress data for process adjustment or certification.
• R&D and Process Development: Assists in optimizing plating formulas and techniques to minimize detrimental stress levels in prototype or new product development.
• Component Manufacturing: Ensures that critical components like connectors, fasteners, and electronic parts receive coatings that meet stringent mechanical and corrosion-resistance requirements.
• Failure Analysis: Helps identify root causes of coating failures related to improper internal stress management.

Related Standards

ASTM B975-22 references other standards and practices related to measurement and safety, helping laboratories and manufacturers maintain consistency and compliance:

• ASTM B636: Test Method for Measurement of Internal Stress of Plated Metallic Coatings with the Spiral Contractometer.
• ASTM E177: Practice for Use of Precision and Bias in ASTM Test Methods.
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method.
• IEC 61010: Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use.

Practical Value

Utilizing ASTM B975-22 in quality assurance workflows helps manufacturers:

• Detect and minimize internal stresses that could lead to coating failures.
• Optimize production parameters for durable, high-performance metallic coatings.
• Fulfill industry and customer requirements regarding coating reliability.
• Reduce warranty claims and improve customer satisfaction with robust, long-lasting components.

Keywords: metallic coatings, internal stress measurement, deposit stress analyzer, ASTM B975-22, electroplating quality control, split strip method, tensile stress, compressive stress, coating durability, industrial plating standards.

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: B975 − 22
Standard Test Method for
Measurement of Internal Stress of Metallic Coatings by Split
Strip Evaluation (Deposit Stress Analyzer Method)
This standard is issued under the fixed designation B975; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The split strip method provides a determination of the internal tensile and compressive stress in
metallic and nonmetallic coatings. Internal stress is expressed in pounds per square inch or
megapascals.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method for determining the internal tensile or
B636Test Method for Measurement of Internal Stress of
compressive stress in applied coatings is quantitative. It is
Plated Metallic Coatings with the Spiral Contractometer
applicable to metallic layers that are applied by the processes
E177Practice for Use of the Terms Precision and Bias in
of electroplating or chemical deposition that exhibit internal
ASTM Test Methods
tensile or compressive stress values from 200psi to 145 000
E691Practice for Conducting an Interlaboratory Study to
psi (1.38MPa to 1000 MPa).
Determine the Precision of a Test Method
1.2 Units—The values stated in either SI units or inch-
3. Terminology
pound units are to be regarded separately as standard. The
values stated in each system are not necessarily exact equiva- 3.1 Definitions of Terms Specific to This Standard:
lents; therefore, to ensure conformance with the standard, each 3.1.1 average deposit thickness, n—the deposit weight in
grams divided by the specific gravity of the deposit in grams
system shall be used independently of the other. Conversion
per cubic centimetre multiplied by the plated deposit surface
between unit systems may result in errors that can cause
area per test strip (see Eq 2).
confusion and should be avoided.
3.1.2 constant K, n—this certifiable calibrated number is
1.3 This standard does not purport to address all of the
determined experimentally for each material lot of test strips
safety concerns, if any, associated with its use. It is the
manufacturedtoenablesimplemathematicalcalculationofthe
responsibility of the user of this standard to establish appro-
internal deposit stress while factoring the influence of the
priate safety, health, and environmental practices and deter-
percent elongation difference between the deposit and the
mine the applicability of regulatory limitations prior to use.
substrate without the use of complicated bent strip formulas.
1.4 This international standard was developed in accor-
See Section 10.
dance with internationally recognized principles on standard-
3.1.3 internal stress, n—stress in a given layer of coating
ization established in the Decision on Principles for the
can result from foreign atoms or materials in the layer that
Development of International Standards, Guides and Recom-
stressthenaturalstructureofthedepositasthecoatingisbeing
mendations issued by the World Trade Organization Technical
formed from sources independent of foreign atoms such as
Barriers to Trade (TBT) Committee.
misfit dislocations and the result of additional processing.
3.1.3.1 compressive stress (-), n—stressthattendstocausea
deposit to expand.
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2022. Published December 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 2015. Last previous edition approved in 2018 as B975–18 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0975-22. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B975 − 22
3.1.3.2 tensile stress (+), n—stress that tends to cause a
deposit to contract.
3.1.3.3 Discussion—Stress that develops in a given layer of
materialismeasuredaspoundspersquareinchormegapascals
where 1 MPa = 145 psi.
3.1.4 modulus of elasticity, n—stress required to produce
unit strain, which may be a change in length (Young’s
modulus), a twist of shear (modulus of rigidity or modulus of
torsion), or a change in volume (bulk modulus).
3.1.5 sample test strip, n—test strip that is used to set the
desired amperage on the power supply. This can be a previ-
ously used test strip.
3.1.6 units spread, n—theamountofdeflectionbetweentest
strip legs is the value of U. Plating test should be continued
until the test strip legs deflect from 2-20 total units spread for
the most accurate results.The U is measured on the measuring
stand.
4. Summary of Test Method
4.1 The first attempt to measure stress values in applied
coatings was the bent strip method, wherein a coating of
known thickness was applied to a strip of flat stock material
having a known modulus of elasticity, length, width, and
thickness. In the test, one end of the strip was held in a fixed
position and one end could bend. The degree of bend experi-
enced by the test strip was then measured. Equations were
proposed by Stoney, Barklie, and Davies ; Heussner, Balden,
4 5
FIG. 1 Test Strip Parameters
and Morse ; and Brenner and Senderoff for this method of
1in.=2.54cm
measurement to calculate the internal deposit stress that was
sufficient to cause deflection of the flat stock material.
4.2 Later methods include the use of flat stock material
formed into a helix that contracts or expands as a stressed
coatingisappliedtothebasematerial(spiralcontractometeras
describedinUnitedStatesPatent4,086,154)andadiskformed
from flat stock material that bows outward or inward as a
stressed coating is applied to the base material (stress meter).
4.3 The deposit stress analyzer method for determining the
internal stress value of a given plating uses bent strip technol-
ogy and the formulas devised for calculation of results appli-
cable to this approach. A specific test piece comprises a
selected metallic material that exhibits spring-like properties
with specified dimensions that define an end area split to give
two legs (see Fig. 1). These test strips are coated with a resist,
to prevent deposition on the front of one leg and the back side
FIG. 2 Compressive and Tensile Stressed Test Strips (provided
of the other leg and on both sides above where the legs divide,
by the Specialty Testing and Development Company, PO Box
leaving a space uncoated at the top for the purpose of making
296, Seven Valleys, PA 17360)
electrical contact to the test piece during the plating process.
See Fig. 2. Each test is performed at specific operating 4.3.1 The internal deposit stress is calculated based on the
total number of increments deflection observed from tip to tip
conditions that are usually selected to approximate the condi-
tions for parts being processed in production mode. after plating. This value is determined as the test strip is
suspended above a measuring stand. See Fig. 3. Results are
calculated by use of split strip formulas expressed in pounds
Stoney, G. G., Proceedings of the Royal Society A, Vol 82, No. 172, 1909, p. per square inch. (See Eq 1 and Eq 3.)
553.
Heussner, Balden, and Morse. "Some Metallurgical Aspects of 5. Significance and Use
Electrodeposits," Plating, Vol 35.
5.1 Internal stress in applied coatings exhibits potential to
Brenner, A., and Senderoff, S. Journal of Research of the National Bureau of
Standards, Vol 42, No. 89, 1949. cause a breakdown of resistance to corrosion and erosion as a
B975 − 22
mountedfixture.Itisalsoadaptabletolaboratorystudieswhere
small solution volumes are advantageous. See Fig. 4. This
device supports a single test strip during the deposition
process.
NOTE 2—Anodes are located external to the In-site Plating Device.
6.3 Cells for In-tank Plating (Internal Anodes)—A test
plating cell that includes two anodes of similar size and
composition at an equal distance from the test strip, which can
be immersed into a working bath. The test strip shall have its
own power supply.
6.4 Cells for Laboratory Bench Plating (Internal
Anodes)—A two-section cell used in a laboratory. Where one
section holds the test strip, and two anodes of similar size and
composition at an equal distance from the test strip, and the
othersectionhasapumpandheater.Theteststripshallhaveits
own power supply.
6.5 Anodes—When using the split strip method to evaluate
the internal deposit stress by electroplating a given metal or
metal alloy deposit, two anodes of similar size, shape, and
composition are placed at a similar distance and parallel to the
test strip to allow equal exposure to the negative current.
6.6 Power Supply—Rectifier to supply amperage for plat-
FIG. 3 Deposit Stress Measuring Stand (provided by the Spe-
cialty Testing and Development Company, PO Box 296, Seven ing.
Valleys, PA 17360)
6.7 Test Strip—A metal strip formed from flat stock that
receives the plating of material being evaluated for internal
depositstress.Duringplating,iftheteststriphastwolegsthey
result of the formation of fractures from micro-cracking and
will deflect outward in opposite directions because of their
macro-cracking within the applied coating. This phenomenon
spring-like properties. Each test strip should be selectively
canalsocauseblistering,peeling,reductionoffatiguestrength,
coated with a material that is resistant to attack by most
and loss. The resulting stress can be tensile in nature, causing
solutions. This coating serves as a mask to define the area to
the deposit to contract, or compressive in nature, causing the
receive deposit materials for tests. See Fig. 1.
deposit to expand.
5.2 To maintain quality assurance by the bent strip method,
it is necessary to monitor production processes for acceptable
levels of internal deposit stress in applied coatings. Most low
values are false. Initial values tend to be lower than the actual
valuebecauseoftheeffectofstockmaterialedgeburrsandthe
resistance of the stock material to bending. Excessive deposit
thickness causes lower-than-true value since the coating over-
powers and changes the initial modulus of elasticity of the test
piece, which becomes more difficult to bend as the coating
continues to build upon it. This phenomenon can be corrected
considerablybyuseofaformulathatcompensatesformodulus
of elasticity differences between the deposit and the substrate
materials, but it does remain a factor. See Eq 3.
NOTE 1—The highest value of the internal deposit stress as obtained on
a stress-versus-plating-thickness curve is usually the truest value of the
internal deposit stress.
6. Apparatus
6.1 Measuring Stand—This stand has a logarithmic scale
over which a test strip is suspended to determine the units
spread as the value of U between the test strip leg tips caused
by the induced deposit stress. (See Fig. 3, Eq 4, and Eq 3.)
6.2 In-site Plating Device for In-tank—This device is a
cylindrical tube that is designed with an adjustable bracket to
FIG. 4 In-site Device (provided by the Specialty Testing and De-
enableplacementofthecellinaworkingtankasapermanently velopment Company, PO Box 296, Seven Valleys, PA 17360)
B975 − 22
NOTE 3—If the deposit stress is tensile in nature, the test strip legs will
8.2 Put a test strip in a soak cleaner solution at 110°F –
deflect with the deposit facing outward. If the deposit stress is
120°F for 30 seconds, then water rinse.
compressive, the deposit will face inward. See Fig. 2.
8.3 Immersetheteststripina10%byvolumehydrochloric
NOTE 4—After a test has been completed, a measurement of total
deflection at the test strip leg tips is determined and the stress value is
acid solution for 15 seconds at room temperature, then water
calculated by the use of equations. See Eq 3.
rinseandisopropylalcoholrinse.Drytheteststripgentlylying
6.8 Copper-iron Alloy Test Strips—These strips are made flat with a paper towel and weigh the test strip. Record the
from UNS Alloy C19400-H02 material. They are 0.00200in.
individualteststripstartingweight(SW)ingramstothefourth
6 0.00005 in. (0.00508cm 6 0.000127cm) thick and are decimal place.
applicable for determining internal deposit tensile or compres-
8.4 Turn the agitation pump ON and set the timer for the
sive stress values between 1500psi and 145000 psi (6.9MPa
required plating time.
and 1000 MPa).
8.5 Attach the weighed test strip so it is centered between
6.9 Pure Nickel Test Strips—These test strips are 0.0011in.
the cell walls.
60.00005in.(0.00279cm 60.000127cm)thick,andtheyare
8.6 Set the timer for the desired test time.
useful for internal deposit tensile or compressive stress values
between 200psi and 60 000psi (1.38MPa and 413.69MPa).
8.7 After the test strip is plated, remove the test strip.
6.10 Temperature Controller—A devise that regulates the
8.8 Rinse the test strip in water, and then rinse it in
temperature of the plating solution. isopropyl alcohol.
6.11 Helix—A metal strip approximately 0.01 in. to 8.9 Dry the test strip gently lying flat with a paper towel.
0.013in. (0.025cm to 0.033 cm) thick formed as a helix
8.10 Place the test strip on the Measuring Stand and record
approximately 0.9in. (2.3 cm) in diameter and 6.1in. (15.5
thetotalunitsspreadasthevalueforU.ThiswillbeusedinEq
cm) long with or without a polytetrafluoroethylene (PTFE)
3 below. Example: 2.4 + 3.1= 5.5 (U)
coating on the inside surface.
8.11 Weigh the plated test strip and record the final weight
7. Equipment Set Up For Laboratory Settings (See Fig.
(see 8.3). Subtract the starting weight (SW) from the final
5)
weight (FW) where the difference = W. This is the W value in
the T=formula (Eq 2).
7.1 Plug the rectifier into the automatic timer.
FW 2SW 5W (1)
7.2 Placetheanodesinthedoublesectionplatingcellanode
pockets and connect the red positive leads to the anodes. 8
9. Test Strip Calculations
7.3 Placetheheater,ifneeded,inthedoublesectionplating
9.1 Calculate the deposit thickness for each test strip using
cell. Plug the heater into an electrical source or a temperature
the following equation:
controller.
W
T 5 5inches (2)
7.4 Set the pump, if needed, to its lowest setting and fasten
D 7.74 cm ! 2.54 cm⁄in.
~ ~ !
it to the non-testing side of the double section plating cell so
where:
the bath will circulate.Agitation in the plating side of the cell
must be limited to prevent the test strip legs from swaying to
T = deposit thickness in inches,
favor one anode over the other. W = weight in grams of the deposit,
D = density of the plated material specific gravity as
7.5 Fillthecellwiththeplatingsolutiontowithina ⁄2in.of
g/cm³, and
the top of the double section plating cell.
2 2
7.74 cm = theplatedsurfaceareaoftheTeststripis1.2in.
7.6 Plug the pump into an electrical source.
(7.74 cm ).
NOTE 5—The 7.74 cm² is based off the measurements in Fig. 1.
7.7 Heat the plating solution to the required operating
temperature.
9.2 After the deposit thickness and the number units spread
has been determined, the deposit stress can be calcu
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: B975 − 18 B975 − 22
Standard Test Method for
Measurement of Internal Stress of Metallic Coatings by Split
Strip Evaluation (Deposit Stress Analyzer Method)
This standard is issued under the fixed designation B975; 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.
ε NOTE—Footnote 5 was editorially corrected in February 2020.
INTRODUCTION
The deposit stress analyzer split strip method provides a rapid, accurate, and economical means for
the determination of the internal tensile and compressive stress in metallic and nonmetallic coatings.
Internal stress is expressed in pounds per square inch or megapascals. This procedure for measuring
internal stress offers the advantages of test specimens that are pre-calibrated by the manufacturer, a
small test specimen coating surface area, and rapid determination of the internal stress in the applied
coating.
1. Scope Scope*
1.1 This test method for determining the internal tensile or compressive stress in applied coatings is quantitative. It is applicable
to metallic layers that are applied by the processes of electroplating or chemical deposition that exhibit internal tensile or
compressive stress values from 200200 psi to 145 000 psi (1.38(1.38 MPa to 1000 MPa).
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.other. Conversion between unit systems may
result in errors that can cause confusion and should be avoided.
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.
2. Referenced Documents
2.1 ASTM Standards:
B636 Test Method for Measurement of Internal Stress of Plated Metallic Coatings with the Spiral Contractometer
This test method is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test
Methods.
Current edition approved Dec. 1, 2018Nov. 1, 2022. Published January 2019December 2022. Originally approved in 2015. Last previous edition approved in 20152018
ɛ1
as B975 – 15.B975 – 18 . DOI: 10.1520/B0975-18E01.10.1520/B0975-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B975 − 22
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 IEC Standard:
IEC 61010 Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 average deposit thickness, n—average deposit thickness equals the deposit weight in grams divided by the specific gravity
of the deposit in grams per cubic centimetre multiplied by the plated deposit surface area per test strip (see Eq 32).
3.1.2 constant K, n—this certifiable calibrated number is determined experimentally for each material lot of test strips
manufactured to enable simple mathematical calculation of the internal deposit stress while factoring the influence of the percent
elongation difference between the deposit and the substrate without the use of complicated bent strip formulas. See Note 4 in
Section 810.
3.1.3 helix, n—metal strip approximately 0.01 to 0.013 in. (0.025 to 0.033 cm) thick formed as a helix approximately 0.9 in. (2.3
cm) in diameter and 6.1 in. (15.5 cm) long with or without a polytetrafluoroethylene (PTFE) coating on the inside surface.
3.1.4 in-site device, n—this device holds a test strip during the application of a coating.
3.1.4.1 Discussion—
Anodes are located external to the specimen holder.
3.1.3 internal stress, n—stress in a given layer of coating can result from foreign atoms or materials in the layer that stress the
natural structure of the deposit as the coating is being formed from sources independent of foreign atoms such as misfit dislocations
and the result of additional processing.
3.1.3.1 compressive stress (-), n—stress that tends to cause a deposit to expand.
3.1.3.2 tensile stress (+), n—stress that tends to cause a deposit to contract.
3.1.3.3 Discussion—
Stress that develops in a given layer of material is measured as pounds per square inch or megapascals where 1 MPa = 145 psi.
3.1.6 measuring stand, n—this stand supports the test strip above a logarithmic scale that enables determination of the total number
of increments spread between the test strip leg tips.
3.1.4 modulus of elasticity, n—stress required to produce unit strain, which may be a change in length (Young’s modulus), a twist
of shear (modulus of rigidity or modulus of torsion), or a change in volume (bulk modulus).
3.1.8 power supply, n—rectifier to supply amperage for plating.
3.1.9 self-contained plating cell, n—this cell contains two anodes within the cell at an equal distance from the test strip that are
suspended in electrolyte for deposition to occur. A section for a heating coil and a pump for solution agitation is an option.
3.1.5 sample test strip, n—metal strip formed from flat stock that receives the coating of material being evaluated for internal
stress.test strip that is used to set the desired amperage on the power supply. This can be a previously used test strip.
3.1.6 units spread, n—the amount of deflection between test strip legs is the value of U. Plating test should be continued until the
test strip legs deflect from 2-20 total units spread for the most accurate results. The U is measured on the measuring stand.
4. Summary of Test Method
4.1 The first attempt to measure stress values in applied coatings was the bent strip method, wherein a coating of known thickness
was applied to a strip of flat stock material having a known modulus of elasticity, length, width, and thickness. In the test, one end
of the strip was held in a fixed position and one end could bend. The degree of bend experienced by the test strip was then
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3 4
measured. Equations were proposed by Stoney, Barklie, and Davies;Davies Houssner,; Heussner, Balden, and Morse;Morse ; and
Brenner and Senderoff for this method of measurement to calculate the internal deposit stress that was sufficient to cause
deflection of the flat stock material.
4.2 Later methods include the use of flat stock material formed into a helix that contracts or expands as a stressed coating is applied
to the base material (spiral contractometer as described in United States Patent 4,086,154) and a disk formed from flat stock
material that bows outward or inward as a stressed coating is applied to the base material (stress meter).
4.3 The deposit stress analyzer method for determining the internal stress value of a given plating uses bent strip technology and
the formulas devised for calculation of results applicable to this approach. A specific test piece comprises a selected metallic
material that exhibits spring-like properties with specified dimensions that define an end area split to give two legs (see Fig. 1).
These test strips are coated with a resist, to prevent deposition on the front of one leg and the back side of the other leg and on
both sides above where the legs divide, leaving a space uncoated at the top for the purpose of making electrical contact to the test
piece during the plating process. See Fig. 2. Each test is performed at specific operating conditions that are usually selected to
approximate the conditions for parts being processed in production mode.
4.3.1 The internal deposit stress is calculated based on the total number of increments deflection observed from tip to tip after
plating. This value is determined as the test strip is suspended above a measuring stand. See Fig. 3. Results are calculated by use
of a simple deposit stress analyzer formula split strip formulas expressed in pounds per square inch. See(See Eq 21 and Eq 3.)
FIG. 1 Test Strip Parameters
1 in. = 2.54 cm
Available from International Electrotechnical Commission (IEC), 3, rue de Varembé, P.O. Box 131, 1211 Geneva 20, Switzerland, http://www.iec.ch.Stoney, G. G.,
Proceedings of the Royal Society A, Vol 82, No. 172, 1909, p. 553.
Heussner, Balden, and Morse. "Some Metallurgical Aspects of Electrodeposits," Plating, Vol 35.
Brenner, A., and Senderoff, S. Journal of Research of the National Bureau of Standards, Vol 42, No. 89, 1949.
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FIG. 2 Compressive and Tensile Stressed Test Strips (provided by the Specialty Testing and Development Company, PO Box 296,
Seven Valleys, PA 17360)
5. Significance and Use
5.1 Internal stress in applied coatings exhibits potential to cause a breakdown of resistance to corrosion and erosion as a result
of the formation of fractures from micro-cracking and macro-cracking within the applied coating. This phenomenon can also cause
blistering, peeling, reduction of fatigue strength, and loss. The resulting stress can be tensile in nature, causing the deposit to
contract, or compressive in nature, causing the deposit to expand.
5.2 To maintain quality assurance by the bent strip method, it is necessary to monitor production processes for acceptable levels
of internal deposit stress in applied coatings. Note that the highest value of the internal deposit stress as obtained on a
stress-versus-plating-thickness curve is usually the truest value of the internal deposit stress. Most low values are false. Initial
values tend to be lower than the actual value because of the effect of stock material edge burrs and the resistance of the stock
material to bending. Excessive deposit thickness causes lower-than-true value since the coating overpowers and changes the initial
modulus of elasticity of the test piece, which becomes more difficult to bend as the coating continues to build upon it. This
phenomenon can be corrected considerably by use of a formula that compensates for modulus of elasticity differences between the
deposit and the substrate materials, but it does remain a factor. See Eq 23.
NOTE 1—The highest value of the internal deposit stress as obtained on a stress-versus-plating-thickness curve is usually the truest value of the internal
deposit stress.
6. Apparatus
6.1 Deposit Stress Analyzer Measuring Stand—This stand has a logarithmic scale over which a test strip is suspended to determine
the increments of units spread as the value of U between the test strip leg tips caused by the induced deposit stress. See(See Fig.
43. See , Eq 14, and Eq 23.)
6.2 In-site Plating Device for In-tank or Laboratory Bench Plating (External Anodes)—In-tank—This device does not hold a
plating bath. It is a 0.875 in. (2.22 cm) diameter, is a cylindrical tube that is designed with an adjustable bracket to enable placement
of the cell in a working tank as a permanently mounted fixture. It is also amenableadaptable to laboratory studies where small
solution volumes are advantageous. See Fig. 34. This device supports a single test strip during the deposition process. To
electroplate a test strip, the existing tank anodes may be used for the test if they are of similar composition and size and are located
equally distant and parallel to the device open ports. Using a rectifier that is separate from the power supply used to plate the parts,
connect the positive lead to each of the two selected tank anodes, and the negative lead to the top of the test strip at the crossbar
that extends over the top of the device. The bottom of the device is sufficiently closed to prevent the test strip from dropping
through. It is critical that the test strip legs do not pass through the side openings as a test strip is placed inside the device. Adjust
the test strip into position against the bottom of the device and approximately 4 in. (10 cm) below the solution level. A 0-1 to 0-2
amp output constant amperage and constant voltage power supply is recommended to control the amperage accurately. The
negative lead from a power supply is then connected to the test strip at the crossbar located at the top of the device. When using
deposition conditions similar to work that is processed in the work tank, the stress measurement result will represent the condition
of the work being processed. The device may also be used on a laboratory table in a container for a plating bath as small as 400
mL in which two small nickel anodes are positioned each across from a device side opening. See Fig. 3. This becomes helpful and
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FIG. 43 Deposit Stress Measuring Stand (provided by the Specialty Testing and Development Company, PO Box 296, Seven Valleys, PA
17360)
FIG. 34 In-site Device (provided by the Specialty Testing and Development Company, PO Box 296, Seven Valleys, PA 17360)
economical when the plating solution is undergoing laboratory studies in regard to additions of multiple additives, particularly if
precious metals are involved. In-tank deposit stress testing yields similar results to those determined on a laboratory bench setup
when the test parameters are similar. However, the deposit stress will vary over a given part, particularly over parts that are
electroformed where the low-current density area deposits usually exhibit the highest deposit stress. In such cases, the determined
deposit stress becomes an approximate average value that serves as a quality control procedure.
NOTE 2—Anodes are located external to the In-site Plating Device.
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6.3 Cells for In-tank Plating or Laboratory Bench Plating (Internal Anodes)—When agitation and solution temperature are not
needed for tests, a A test plating cell that includes two anodes of similar size and composition at an equal distance from the test
piece is recommended. When solution agitation and elevated bath temperature are required, a two-section cell could be used where
one side has a pump and heater. Cells with open low side ports would permit immersion strip, which can be immersed into a
working bath allowing the cell to fill as it is being lowered. bath. The test strip shall have its own power supply. In these cells,
a test strip is suspended at the center of the cell by clipping its top end to a stainless steel cross support bar. Two anodes 2 ⁄8 ×
3 1
2 ⁄8 × ⁄8 in. (6 × 6 × 0.3 cm) are positioned along the end of the cell walls where anode pockets are attached. These cells can be
designed to be hung directly in a working tank or they could be used in a laboratory setup.
6.4 Cells for Laboratory Bench Plating (Internal Anodes)—A two-section cell used in a laboratory. Where one section holds the
test strip, and two anodes of similar size and composition at an equal distance from the test strip, and the other section has a pump
and heater. The test strip shall have its own power supply.
6.5 Anodes—When using the deposit stress analyzer split strip method to evaluate the internal deposit stress by electroplating a
given metal or metal alloy deposit, two anodes of similar size, shape, and composition are placed at a similar distance from the
test strip in a position and parallel to the test strip to allow equal exposure of the test strip to the negative current. The positive
lead from the power supply shall be connected to each anode.
6.6 Container—Power Supply—For tabletop setups, a suitable container can be used to hold a plating bath selected for evaluation
when using the in-tank plating cells that have bottom holes for solution flow. Rectifier to supply amperage for plating.
6.7 Test Strips—Strip—Test strips are used to receive an applied coating that is under investigation for the determination of A metal
strip formed from flat stock that receives the plating of material being evaluated for internal deposit stress. Test strips are shaped
similar to a tuning fork so that During plating, if the test strip legs exist in the same plane geometrically. During the application
of a stressed coating, the test strip legs has two legs they will deflect outward in opposite directions. They are made from materials
that exhibit spring-like properties so the plated test strip legs will return to the as-plated position if deflected or disturbed by minor
mishandling before the degree of deflection is determined.directions because of their spring-like properties. Each test strip is should
be selectively coveredcoated with an organic a material that is resistant to attack by most solutions to which the test strips are
exposed. solutions. This coating serves as a mask to define the area to receive deposit materials for tests. See Fig. 1.
NOTE 1—Strong alkaline solutions could dissolve away the resist material that covers the areas that do not receive the deposit. If this occurs, a thin coat
of high-solids, air-dry lacquer such as Micro-Shield diluted with acetone in a one-to-one ratio is applied by an artist brush over that specific area. When
dry, the test can proceed. If lacquer is removed during the test, oven baking at 180 °F (82 °C) for two hours will increase the adhesion of the lacquer.
NOTE 3—If the deposit stress is tensile in nature, the test strip legs will deflect with the deposit facing outward. If the deposit stress is compressive, the
deposit will face inward. See Fig. 2.
NOTE 4—After a test has been completed, a measurement of total deflection at the test strip leg tips is determined and the stress value is calculated by
the use of a simple equation. equations. See Eq 23.
6.8 Copper-iron Alloy Test Strips—These strips are made from UNS Alloy C19400-H02 material. TheseThey are
0.002000.00200 in. 6 0.00005 in (0.00508in. (0.00508 cm 6 0.000127 cm) thick. Theythick and are applicable for determining
internal deposit tensile or compressive stress values between 15001500 psi and 145 000 psi (6.9(6.9 MPa and 1000 MPa). When
used to evaluate chemically induced electroless deposits, a watts or sulfamate nickel strike for 30 s at 0.25 amps, 33 asf may be
required to activate the surface for metallic deposition.
6.9 Pure Nickel 99 % Cold-rolled Test Strips—These test strips are 0.00110.0011 in. 6 0.00005 in. (0.00279(0.00279 cm 6
0.000127 cm) thick. They thick, and they are useful for internal deposit tensile or compressive stress values between 200200 psi
and 60 000 psi (1.38 and 413.69 MPa). They are the most sensitive test strip choice for low stress conditions and have a wide range
of applications, the primary one being electroless nickel deposits that can be applied by a chemical reduction process. For some
bath formulations, an activation step may be required, such as a brief dip in diluted hydrochloric acid or plated in a woods nickel
strike. When these test strips are used for testing nickel deposits, in a nickel-over-nickel situation, the substrate has little influence
on the initial internal deposit stress of the applied coating. (1.38 MPa and 413.69 MPa).
6.10 Temperature Controller—A devise that regulates the temperature of the plating solution.
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6.11 Helix—A metal strip approximately 0.01 in. to 0.013 in. (0.025 cm to 0.033 cm) thick formed as a helix approximately 0.9 in.
(2.3 cm) in diameter and 6.1 in. (15.5 cm) long with or without a polytetrafluoroethylene (PTFE) coating on the inside surface.
7. Preparation of Test Strips for Calibration and Use
7.1 Test strips must be in a precleaned condition with soils and oils removed prior to plating. Immerse the areas for coating on
the test strip legs in a mild aqueous soak cleaning solution for 30 s. This step is followed with a water rinse. Immerse the test strip
in a dilute mineral acid solution such as 10 % by volume hydrochloric acid for 30 s to remove surface oxides, and then water rinse.
7. Equipment Set Up For Laboratory Settings (See Fig. 5)
7.1 Plug the rectifier into the automatic timer.
7.2 Place the anodes in the double section plating cell anode pockets and connect the red positive leads to the anodes.
7.3 Place the heater, if needed, in the double section plating cell. Plug the heater into an electrical source or a temperature
controller.
7.4 Set the pump, if needed, to its lowest setting and fasten it to the non-testing side of the double section plating cell so the bath
will circulate. Agitation in the plating side of the cell must be limited to prevent the test strip legs from swaying to favor one anode
over the other.
7.5 Fill the cell with the plating solution to within a ⁄2 in. of the top of the double section plating cell.
7.6 Plug the pump into an electrical source.
7.7 Heat the plating solution to the required operating temperature.
7.8 Connect the red positive lead from the power supply to the anode contact provided on the cell (lug to connect red wires).
7.9 Follow the test procedure (see Section 8 and Fig. 5).
7.10 Then use the black negative lead to fasten a test strip to the test strip clip on the double section plating cell.
8. Calibration of Test Strips
8.1 To determine the internal deposit stress in metallic coatings applied to test strips, it is necessary to establish a standardized
deposit stress value from which a constant designated as K can be assigned. This value includes and combines the various forces
that induce stress and strain and influence the bendability of the test strip legs. When used to determine stress values, each material
lot of test strips manufactured responds differently because of slight variations in stock thickness that occur during the rolling
process, temper, and particularly the large differences in material percentages of elongation over the 3 in. (7.6 cm) length of the
test strip legs. To compensate for these differences, the constant is designated as K in a certified manner for each material lot of
test strips manufactured. Test strips are calibrated by the manufacturer as a two-step procedure where the deposit stress of a selected
nickel plating bath is used to plate three test strips and two helices. This K value is included in the formulas that are used to
determine the internal stress of applied coatings in pounds per square inch.
8.2 When the internal deposit stress value has been determined as in 8.1 the constant K can be obtained using the following
formula:
K 5 3 TS ÷ UM (1)
The content of this section was provided by Specialty Testing and Development Company, PO Box 296, Seven Valleys, PA 17360.
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FIG. 5 Double Cell Set Up (provided by Specialty Testing and Development Company, PO Box 296, Seven Valleys, PA 17360)
where:
K = calibration constant,
T = average deposit thickness in inches,
S = internal deposit stress as psi, as determined by use of a spiral contractometer test method,
U = average number of increments spread between the test strip leg tips as measured over the deposit stress analyzer scale, and
M = correction for modulus of elasticity differences = modulus of elasticity of the deposit ÷ modulus of elasticity of the substrate
(see Table 1).
8.3 To determine the K factor calibration constant in the split strip equation, K = 3TS/UM, a high nickel sulfate, low nickel
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TABLE 1 Values for M in
...