ASTM B530-02 pdf free.Standard Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Electrodeposited Nickel Coatings on Magnetic and Nonmagnetic Substrates.
Operate each instrument in accordance with the instruc-tions of the manufacturer. Give appropriate attention to thefactors listed in Section 4. Check the calibration of the instrument at the test siteeach time the instrument is put into service,and at regularintervals during use, to assure proper performance.
Observe the following precautions:Basis Metal Thickness (lype A coatings only)—Check whether the basis metal thickness exceeds the criticalthickness.If not, either use the back-up method of 5.5, or makesure that the calibration has been made on a standard havingthe same thickness and magnetic properties as the test specimen.Do not make readings close to an edge,hole,inside corner，etc., of a specimen,unless the validity ofthe calibration for such a measurement has been demonstrated.Do not make readings on a curved surfaceof a specimen, unless the validity of the calibration for such ameasurement has been demonstrated.Number of Readings:For each measurement，make at least 3 readings,removing the probe after each reading,and average thereadings.If any 2 of the readings differ from each other bymore than 5 % of the average reading or 2 um, whichever is thegreater, then the measurement shall be discarded and repeated.6.3.4.2 The substrate or coating, or both, may be too roughto meet this criterion. In such a case it may be possible toobtain a valid measurement by averaging a number of readings.To be valid under this test method,the validity of such aprocedure must be demonstrated (see Appendix X1). Instruments of the attractive force type are sensitiveto vibrations, and readings that are obviously erroneous shouldbe rejected.
In general, place the instrument probe perpendicularto the specimen surface at the point of measurement. For someinstruments of the attractive force type, this is essential. Withsome instruments，however,it is desirable to tilt the probeslightly and select the angle of inclination giving the minimumreading.If, on a smooth surface, the readings obtained varysubstantially with the angle of inclination, it is probable thatthe probe is worn and needs to be replaced. If a magneticinstrument is to be used in horizontal or upside-down position,calibrate it for that position.ASTM B530 pdf download.