ASTM B567-98(2009a)
(Test Method)Standard Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
Standard Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
SIGNIFICANCE AND USE
The thickness or mass per unit area of a coating is often critical to its performance.
For some coating-substrate combinations, the beta backscatter method is a reliable method for measuring the coating nondestructively.
The test method is suitable for thickness specification acceptance if the mass per unit area is specified. It is not suitable for specification acceptance if the coating thickness is specified and the density of the coating material can vary or is not known.
SCOPE
1.1 This test method covers the beta backscatter gages for the nondestructive measurement of metallic and nonmetallic coatings on both metallic and nonmetallic substrate materials.
1.2 The test method measures the mass of coating per unit area, which can also be expressed in linear thickness units provided that the density of the coating is known.
1.3 The test method is applicable only if the atomic numbers or equivalent atomic numbers of the coating and substrate differ by an appropriate amount (see 6.2).
1.4 Beta backscatter instruments employ a number of different radioactive isotopes. Although the activities of these isotopes are normally very low, they can present a hazard if handled incorrectly. This standard does not purport to address the safety issues and the proper handling of radioactive materials. It is the responsibility of the user to comply with applicable State and Federal regulations concerning the handling and use of radioactive material. Some States require licensing and registration of the radioactive isotopes.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: B567 − 98 (Reapproved2009a)
Standard Test Method for
Measurement of Coating Thickness by the Beta Backscatter
1
Method
This standard is issued under the fixed designation B567; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope emitting energy or particles, or both. This process is known as
radioactive decay.The total number of disintegrations during a
1.1 This test method covers the beta backscatter gages for
suitably small interval of time divided by that interval of time
the nondestructive measurement of metallic and nonmetallic
is called “activity.” Therefore, in beta backscatter
coatings on both metallic and nonmetallic substrate materials.
measurements, a higher activity corresponds to a greater
1.2 The test method measures the mass of coating per unit
emissionofbetaparticles.Theactivityofaradioactiveelement
area, which can also be expressed in linear thickness units
used in beta backscatter gages is generally expressed in
4
provided that the density of the coating is known.
microcuries (1 µCi=3.7×10 disintegrations per second).
1.3 Thetestmethodisapplicableonlyiftheatomicnumbers
2.1.2 aperture—the opening of the mask abutting the test
or equivalent atomic numbers of the coating and substrate
specimen. It determines the size of the area on which the
differ by an appropriate amount (see 6.2).
coating thickness is measured. This mask is also referred to as
a platen, an aperture plate, a specimen support, or a specimen
1.4 Beta backscatter instruments employ a number of dif-
mask.
ferent radioactive isotopes. Although the activities of these
isotopes are normally very low, they can present a hazard if
2.1.3 backscatter—when beta particles pass through matter,
handled incorrectly. This standard does not purport to address
they collide with atoms. Among other things, this interaction
the safety issues and the proper handling of radioactive
will change their direction and reduce their speed. If the
materials. It is the responsibility of the user to comply with
deflections are such that the beta particle leaves the body of
applicable State and Federal regulations concerning the han-
matter from the same surface at which it entered, the beta
dling and use of radioactive material. Some States require
particle is said to be backscattered.
licensing and registration of the radioactive isotopes.
2.1.4 backscatter coeffıcient—the backscatter coefficient of
1.5 The values stated in SI units are to be regarded as a body, R, is the ratio of the number of beta particles
standard. No other units of measurement are included in this
backscattered to that entering the body. R is independent of the
standard. activity of the isotope and of the measuring time.
1.6 This standard does not purport to address all of the
2.1.5 backscatter count:—
safety concerns, if any, associated with its use. It is the 2.1.5.1 absolute backscatter count—the absolute backscat-
responsibility of the user of this standard to establish appro-
ter count, X, is the number of beta particles that are backscat-
priate safety and health practices and determine the applica- tered during a finite interval of time and displayed by the
bility of regulatory limitations prior to use.
instrument. X will, therefore, depend on the activity of the
source, the measuring time, the geometric configuration of the
2. Terminology
measuringsystem,andthepropertiesofthedetector,aswellas
2.1 Definitions of Terms Specific to This Standard: the coating thickness and the atomic numbers of the coating
2.1.1 activity—the nuclei of all radioisotopes are unstable and substrate materials. X is the count produced by the
0
and tend to change into a stable condition by spontaneously uncoated substrate, and Xs, that of the coating material. To
obtainthesevalues,itisnecessarythatboththesematerialsare
available with a thickness greater than the saturation thickness
1
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
(see 2.1.12).
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.10 on
Test Methods.
2.1.5.2 normalized backscatter—the normalized
Current edition approved Sept. 1, 2009. Published December 2009. Originally
backscatter, x , is a quantity that is independent of the activity
approved in 1972. Last previous edition approved in 2009 as B567 – 98 (2009). n
DOI: 10.1520/B0567-98R09. of the source, the measuring time, and the properties of the
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