1、Designation: B530 09 (Reapproved 2014)Standard Test Method forMeasurement of Coating Thicknesses by the MagneticMethod: Electrodeposited Nickel Coatings on Magnetic andNonmagnetic Substrates1This standard is issued under the fixed designation B530; the number immediately following the designation in
2、dicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies
3、of the U.S. Department of Defense.1. Scope1.1 This test method covers the use of magnetic instrumentsfor the nondestructive measurement of the thickness of anelectrodeposited nickel coating on either a magnetic or non-magnetic substrate. It is intended to supplement manufacturersinstructions for the
4、 operation of the instruments and is notintended to replace them.1.2 These instruments measure either the magnetic attrac-tion between a magnet and the coating-substrate combination(categorized as “magnetic pull-off”), or the change in magneticflux density within the probe (categorized as “electroni
5、c”).1.3 For this test method, there are two types of coating-substrate combinations that can be encountered: TypeA, nickelcoatings on a magnetic substrate, and Type B, nickel coatingson a nonmagnetic substrate.1.4 The effective measuring ranges of instruments using theprinciple of magnetic attractio
6、n are up to 50 m (2 mils) forType A coatings, and up to 25 m (1 mil) for Type B coatings.For gages based on change in magnetic flux density principles,the effective ranges are much greater, and measurements up to1 mm (40 mils) or more, can be made on both types ofcoatings.1.5 Measurements made in ac
7、cordance with this test methodwill be in compliance with the requirements of ISO Stan-dard 2361 as printed in 1982.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 This standard does not purport to address all of thesafe
8、ty concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B487 Test Method for Measurement
9、 of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB504 Test Method for Measurement of Thickness of Metal-lic Coatings by the Coulometric MethodB74
10、8 Test Method for Measurement of Thickness of Metal-lic Coatings by Measurement of Cross Section with aScanning Electron Microscope2.2 ISO International Standard:ISO 2361 Electrodeposited Nickel Coatings on Magneticand Nonmagnetic SubstratesMeasurement of CoatingThicknessMagnetic Method33. Terminolo
11、gy3.1 Definitions of Terms Specific to This Standard:3.1.1 accuracy, nthe measure of the magnitude of errorbetween the result of a measurement and the true thickness ofthe item being measured.3.1.2 adjustment, nthe physical act of aligning an instru-ments thickness readings to match those of a known
12、 thicknesssample (removal of bias), in order to improve the accuracy ofthe instrument on a specific surface or within a specific portionof its measurement range. An adjustment will affect theoutcome of subsequent readings.1This test method is under the jurisdiction ofASTM Committee B08 on Metallican
13、d Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved May 1, 2014. Published May 2014. Originallyapproved in 1970. Last previous edition approved in 2009 as B530 09. DOI:10.1520/B0530-09R14.2For referenced ASTM standards, visit the ASTM
14、website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036,
15、http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 calibration, nthe high-level, controlled and docu-mented process of obtaining measurements on traceable cali-bration standards over the full operating range of t
16、heinstrument, then making the necessary instrument adjustments(as required) to correct any out-of-tolerance conditions.3.1.3.1 DiscussionCalibration of coating thickness instru-ments is performed by the equipment manufacturer, an autho-rized agent, or by an authorized, trained calibration laboratory
17、in a controlled environment using a documented process. Theoutcome of the calibration process is to restore/realign theinstrument to meet/exceed the manufacturers stated accuracy.3.1.4 reference standard, na specimen of known thicknessused to verify the accuracy of a coating thickness measuringinstr
18、ument.3.1.5 verification of accuracy, nobtaining measurementson a reference standard prior to instrument use for the purposeof determining the ability of the coating thickness instrument toproduce reliable values, compared to the combined instrumentmanufacturers stated accuracy and the stated accura
19、cy of thereference standard.4. Summary of Test Method4.1 Magnetic pull-off instruments are mechanical instru-ments that measure the force required to pull a permanentmagnet from magnetic material. The magnetic force of attrac-tion to the magnetic coating or coating-substrate combinationis opposed by
20、 a spring or coil. Tension is applied to thespring/coil until the magnetic attraction to the material isovercome. The instrument must be placed directly on thecoated surface to obtain a measurement. The force holding thepermanent magnet to the magnetic material is inversely pro-portional to the thic
21、kness of the coating layer(s) between themagnet and the magnetic material. For example, a thin nickellayer applied to a nonmagnetic substrate will require lessspring tension to pull the magnet off than will a thicker nickellayer, since the thinner coating has weaker magnetic strength.4.2 Electronic
22、instruments measure a change in magneticflux density within the probe to produce a coating thicknessmeasurement. The instrument probe must be placed directly (ina perpendicular position) on the coated surface to obtain ameasurement. These instruments determine the effect on themagnetic field generat
23、ed by the probe due to the proximity tothe substrate.5. Significance and Use5.1 The thickness of a coating is often critical to itsperformance. This magnetic method is suitable for measuringnondestructively the thickness of some nickel coatings and forspecification acceptance.5.2 This method require
24、s that the magnetic properties of thecoating and its substrate be the same as those of the referencestandards used for the calibration adjustment of the instrument.5.3 This method should not be used to determine thethickness of autocatalytically deposited nickel-phosphorus al-loys containing more th
25、an 8 % phosphorus on steel. Thosecoatings are sufficiently nonmagnetic for Test Method B499 tobe suitable for that determination, as long as the measurementis made prior to any heat treatment.6. Apparatus6.1 Coating Thickness Instrument , based on magneticprinciples, commercially available, suitable
26、 to measure coatingthickness accurately.6.2 Coating Thickness Standards , with assigned valuestraceable to a National Metrology Institution. They may becoated or plated steel plates, or may be foils or shims of flat,non-metallic sheet (typically polyester).7. Calibration and Standardization7.1 Calib
27、ration of coating thickness instruments is per-formed by the equipment manufacturer, an authorized agent, orby an authorized, trained calibration laboratory in a controlledenvironment using a documented process. A Certificate ofCalibration showing traceability to a National MetrologyInstitution can
28、be issued. There is no standard time interval forre-calibration, nor is one absolutely required, but a calibrationinterval can be established based on experience and the workenvironment. A one-year calibration interval is a typicalfrequency suggested by many instrument manufacturers.7.2 Before use,
29、each instruments calibration accuracy shallbe verified in accordance with the instructions of themanufacturer, employing suitable thickness standards and, ifnecessary, any deficiencies found shall be corrected.7.3 During use, calibration accuracy shall be verified atfrequent intervals, at least once
30、 a day. Attention shall be givento the factors listed in Section 8 and to the proceduresdescribed in Section 9.7.4 Reference standards shall be coated standards obtainedby electroplating nickel adherently onto a substrate. Thecoating thickness of the reference standards shall bracket theusers highes
31、t and lowest coating thickness measurementrequirement.7.5 The substrate and the coating of the standard shall havethe same magnetic properties as those of the test specimen (see8.2, 8.3, 8.11 and 8.12).7.5.1 To assure the similarity of the magnetic properties ofthe nickel deposit and for Type A coat
32、ings on steel substrate,reference standards shall be produced and measured by anothersuitable test method, such as cross sectioning or the coulomet-ric test method from a specimen produced under identicalconditions as the test specimen to be measured. To confirm thesimilarity of the magnetic propert
33、ies of the substrate to those ofthe standards, a comparison of the readings obtained with thebare basis metal of the standard to that of the test specimen isrecommended.7.5.2 In the same manner, the similarity of the magneticproperties of the coating of the test specimen to that of thestandard can b
34、e established by verifying with the crosssectioning (Test Methods B487 or B748) or coulometric (TestMethod B504) methods that the thickness reading obtained onthe test specimen by means of the properly adjusted instrumentcorresponds to the actual thickness determined by one or bothof the above metho
35、ds.B530 09 (2014)27.6 Where indicated, the accuracy of the instrument shouldbe checked by rotating the probe in increments of 90 (see 8.7and 8.8).7.7 For Type A coatings, the basis metal thickness for thetest and the calibration adjustment shall be the same if thecritical thickness, defined in 8.3,
36、is not exceeded. Whenpossible, back up the basis metal of the standard, or the testspecimen, with a sufficient thickness of similar material tomake the readings independent of the basis metal thickness.7.8 If the curvature of the coating to be measured is such asto preclude calibration adjustment on
37、 a flat surface, thecurvature of the coated standard shall be the same as that of thetest specimen.8. Factors Affecting the Measuring Accuracy8.1 Coating ThicknessInherent in the method is a measur-ing uncertainty that, for thin coatings, is constant and indepen-dent of the coating thickness; for th
38、icknesses greater than about50 m (2 mils), this uncertainty is proportional to the coatingthickness.8.2 Magnetic Properties of the Basis Metal (Type A coatingsonly)Magnetic thickness measurements are affected byvariations in the magnetic properties of the basis metal. Forpractical purposes, magnetic
39、 variations in low-carbon steel canoften be considered to be insignificant. To avoid the influencesof severe or localized heat treatments and cold working, theinstrument should be adjusted using a reference standardhaving a basis metal with the same magnetic properties as thatof the test specimen or
40、, preferably and if available, with asample of the part to be tested before application of the coating.8.3 Basis Metal Thickness (Type A coatings only)For eachinstrument, there is a critical thickness of the basis metal abovewhich the measurements will not be affected by an increase inthat thickness
41、. Since it depends on the instrument probe (Note1) and the nature of the basis metal, its value should bedetermined experimentally, if it is not supplied by the manu-facturer.NOTE 1The term “instrument probe” also includes the term “magnet.”8.4 Edge EffectThe method is sensitive to abrupt changesin
42、the surface contour of the test specimen. Therefore, mea-surements made too near an edge or inside corner will not bevalid, unless the instrument is specially adjusted for such ameasurement. This also applies to measurements made ongeometrically limited areas, such as narrow conductors onprinted cir
43、cuit boards.8.5 CurvatureMeasurements are affected by the curvatureof the test specimen. The influence of curvature varies consid-erably with the make and type of instrument, but alwaysbecomes more pronounced as the radius of curvature de-creases. Instruments with two-pole probes may also producedif
44、ferent readings, depending on whether the poles are alignedin planes parallel or perpendicular to the axis of a cylindricalsurface. A similar effect can occur with a single-pole probe, ifthe tip is unevenly worn. Measurements made on curved testspecimens may not, therefore, be valid unless the instr
45、ument isspecifically adjusted for such measurements.8.6 Surface Roughness:8.6.1 Measurements are influenced by the surface topogra-phy of the substrate and the coating, and a rough or scratchedsurface will give individual instrument readings that all varyfrom point to point. In this case, it is nece
46、ssary to make manyreadings at different positions to obtain an average value that isrepresentative of the mean coating thickness.8.6.2 If the basis metal is magnetic and rough, it may also benecessary to check, and adjust if necessary, the zero of theinstrument at several positions on a sample of th
47、e uncoatedrough substrate.8.6.3 If the roughness of the substrate surface is small,relative to the coating thickness, its effect will probably benegligible.8.7 Direction of Mechanical Working of the Basis Metal(Type A coatings only) Measurements made by an instrumenthaving a two-pole probe or an une
48、venly worn single-pole probemay be influenced by the direction in which the magnetic basismetal has been subjected to mechanical working, such asrolling. The reading may change with the orientation of theprobe on the surface.8.8 Residual Magnetism (Type A coatings only)Residualmagnetism in the basis
49、 metal affects the measurements madeby instruments that employ a stationary magnetic field. Itsinfluence on measurements made by reluctance instrumentsemploying an alternating magnetic field is much smaller.8.9 Stray Magnetic FieldStrong stray magnetic fields,such as those produced by various types of electricalequipment, can seriously interfere with the operation of instru-ments based on magnetic principles.8.10 Foreign ParticlesThe probes of magnetic instru-ments of all types must make physical contact with the testsurface and are, therefore, sensitive
