ASTM B – Designation: B – 98 (Reapproved ) UNCONTROLLED (if printed out) Standar. Basic Description: ASTM B X-Ray Fluorescence (XRF) is a non-destructive method of measuring plating thickness by using an X-ray beam to excite the. Designation: B − 98 (Reapproved ) Standard Test Method for This test method is under the jurisdiction of ASTM Committee B08 on Metallic.
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Advanced Plastic and Material Testing, Inc.
Results are reported in a table with five or more readings per sample. The measurement of a coating thickness by X-ray absorption is not applicable if an intermediate coating is present because of the indeterminate absorption effect of intermediate layer. This method sometimes is described as numerical? From six to sixty adjacent channels can be used to store the pulses representing a selected characteristic emission of one element, the number of channels depending on the width of the emission peak usually displayed on the face of a cathode ray tube.
Last previous edition approved in as B — The stated mass per unit area of each coating thickness SRM is certi? Most modern industrial X-ray instrumentation will perform this calculation automatically. Caution must be exercised, however, to see that the use of a large sample area in conjunction with high power input to the X-ray tube does not result in a signal so large as to exceed the count-rate capacity of the detection system.
This method can be used when the energies of the detected characteristic radiations do not differ sufficiently for example, characteristic radiation from Au and Br. This limiting thickness depends, in general, upon the energy of the characteristic X-ray and the density and absorption properties of the material under analysis. Current edition approved June 1, Care must be taken that the coating and substrate are thick enough to prevent the primary X-ray beam from reaching and?
Avoid specimen areas having visible defects such as?
It can be used to measure coating and base combinations that are not readily measured by other techniques. Astj is because both the exciting and secondary characteristic radiations undergo attenuation in passing through the coating. The advantages of radioisotope excitation include more compact instrumentation essentially monochromatic radiation, and very low background intensity.
This type of detector is maintained at a very low temperature in a liquid-nitrogen cryostat 77K. A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval.
With wavelength dispersive systems, the types of detectors commonly used as the gas-? Eastern Applied Research, Inc. A minimum area of 0. Typical examples of such combinations are gold on nickel on copper and nickel on copper on steel.
The SRM shall be measured? The major disadvantage of radioisotope excitation is the much lower intensities available as compared with X-ray tube sources. In consequence, an estimate of the counting rate based on a short counting interval for example, 1 or 2 s may be appreciably different from an estimate based on a longer counting period, particularly if the counting rate is low.
The typical relationship between a atm thickness and the intensity of a characteristic emission from the coating metal is illustrated by the curve in the Appendix, Fig.
Similarly, the detector may also be masked so that it will see only that area of the specimen on which the coating thickness is to be determined. Typically, a channel may represent a span of 20 eV for a lithium-drifted silicon detector or asrm eV for a proportional counter.
Other disadvantages include the limited number of suitable radioisotopes, their rather short useful lifetimes, and the personnel protection problems associated with highintensity radioactive sources. The benefit to operators is that it details the variations in x-ray spectrometry systems and explains how XRF works with some terminology that may be useful. The sources of error will be aatm by the use of calibration standards electroplated in the same type of asmt under the same conditions as those used in the production of the coatings to be 3 Copyright by ASTM Int’l all rights reserved ; Reproduction authorized per License Agreement with Victoria Boyer ; Wed Mar 23 Standards of known thickness are required to astk a calibration curve for each plating and base material combination.
ASTM B568 (measurement of coating thickness by XRF)
Precision and Bias For this reason, signi? The X-ray absorption method cannot be used when one or more intermediate coating layers are present. It is important to note that ASTM B does not detail safety procedures relating to operation of x-ray spectrometry and refers the reader to the appropriate governing bodies and regulations. It also provides an overview of calibration techniques and best practices along with standard-less fundamental parameters calibrations.
ASTM B – PLATING THICKNESS BY XRF TESTING SERVICES
X-ray tubes typically have intensities that are several orders of magnitude greater than radioisotope sources. Published data in tabular form are available that relate spectrogoniometer settings to the characteristic emissions of elements for each of the commonly used analyzing crystals.
Calibration standards having the same radius of curvature as that of the test specimens can also aztm used to eliminate asrm effects. If pores or voids are present, X-ray methods will give an indication of coating mass per unit area but not of thickness. Under such circumstances, thickness measurements must be corrected for density differences, unless density differences can be shown to be insigni? When an energy-dispersive system is being used it should be recognized that a signi?
Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM asmt the above address or at phonefaxor service astm.
These should be used only to calibrate and periodically check the condition asm the working standards. The exciting radiation may be generated by an X-ray tube or by certain radioisotopes. Factors Affecting Accuracy 6. Measurements by this ratio method are largely independent of the distance between test specimen and detector.