ASTM B975-15
(Test Method)Standard Test Method for Measurement of Internal Stress of Metallic Coatings by Split Strip Evaluation (Deposit Stress Analyzer Method)
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. Note that the highest value of the internal deposit stress as obtained on a stress-versus-coating-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 values 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 2.
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 500 to 145 000 psi (3.45 to 1000 MPa).
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B975 − 15
Standard Test Method for
Measurement of Internal Stress of Metallic Coatings by Split
1
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 deposit stress analyzer 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 E691Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method for determining the internal tensile or
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2.2 IEC Standard:
compressive stress in applied coatings is quantitative. It is
IEC 61010Safety Requirements for Electrical Equipment
applicable to metallic layers that are applied by the processes
for Measurement, Control, and Laboratory Use
of electroplating or chemical deposition that exhibit internal
tensile or compressive stress values from 500 to 145 000 psi
3. Terminology
(3.45 to 1000 MPa).
3.1 Definitions of Terms Specific to This Standard:
1.2 The values stated in inch-pound units are to be regarded
3.1.1 average deposit thickness, n—average deposit thick-
as standard. The values given in parentheses are mathematical
nessequalsthedepositweightingramsdividedbythespecific
conversions to SI units that are provided for information only
gravity of the deposit in grams per cubic centimetre multiplied
and are not considered standard.
by the plated deposit surface area per test strip (see Eq 3).
1.3 This standard does not purport to address all of the
3.1.2 constant K, n—this certifiable calibrated number is
safety concerns, if any, associated with its use. It is the
determined experimentally for each lot of test strips manufac-
responsibility of the user of this standard to establish appro-
tured to enable simple mathematical calculation of the internal
priate safety and health practices and determine the applica-
deposit stress while factoring the influence of percent elonga-
bility of regulatory limitations prior to use.
tion difference between the deposit and the substrate without
the use of complicated bent strip formulas. See Note 4.
2. Referenced Documents
3.1.3 helix, n—metal strip approximately 0.01 to 0.013in.
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2.1 ASTM Standards:
(0.025 to 0.033 cm) thick formed as a helix approximately 0.9
B636Test Method for Measurement of Internal Stress of
in. (2.3 cm) in diameter and 0.61 in. (15.5 cm) long with or
Plated Metallic Coatings with the Spiral Contractometer
withoutapolytetrafluoroethylene(PTFE)coatingontheinside
E177Practice for Use of the Terms Precision and Bias in
surface.
ASTM Test Methods
3.1.4 internal stress, n—stress in a given layer of coating
can result from foreign atoms or materials in the layer that
stressthenaturalstructureofthedepositasthecoatingisbeing
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ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
formed from sources independent of foreign atoms such as
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on
misfit dislocations and the result of additional processing.
Test Methods.
Current edition approved Nov. 1, 2015. Published December 2015. DOI:
3.1.4.1 Discussion—Stress that develops in a given layer of
10.1520/B975-15.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on Available from International Electrotechnical Commission (IEC), 3, rue de
the ASTM website. Varembé, P.O. Box 131, 1211 Geneva 20, Switzerland, http://www.iec.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B975 − 15
materialismeasuredaspoundspersquareinchormegapascals 4. Summary of Test Method
where 1 MPa = 145 psi.
4.1 The first attempt to measure stress values in applied
3.1.5 measuring stand, n—this stand supports the test strip
coatings was the bent strip method, wherein a coating of
above a logarithmic scale that enables determination of the
known thickness was applied to a strip of flat stock material
total number
...
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