ASTM B530-09(R2021) pdf free download

ASTM B530-09(R2021) pdf free download.Standard Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Electrodeposited Nickel Coatings on Magnetic and Nonmagnetic Substrates
3.1.2 adjustment, n—the physical act of aligning an instru- ment’s thickness readings to match those of a known thickness sample (removal of bias), in order to improve the accuracy of the instrument on a specific surface or within a specific portion of its measurement range. An adjustment will affect the outcome of subsequent readings.
3.1.3 calibration, n—the high-level, controlled and docu- mented process of obtaining measurements on traceable cali- bration standards over the full operating range of the instrument, then making the necessary instrument adjustments (as required) to correct any out-of-tolerance conditions.
3.1.3.1 Discussion—Calibration of coating thickness instru- ments is performed by the equipment manufacturer, an autho- rized agent, or by an authorized, trained calibration laboratory in a controlled environment using a documented process. The outcome of the calibration process is to restore/realign the instrument to meet/exceed the manufacturer’s stated accuracy.
3.1.4 reference standard, n—a specimen ofknown thickness used to verify the accuracy of a coating thickness measuring instrument.
3.1.5 verification of accuracy, n—obtaining measurements on a reference standard prior to instrument use for the purpose ofdetermining the ability ofthe coating thickness instrument to produce reliable values, compared to the combined instrument manufacturer’s stated accuracy and the stated accuracy of the reference standard.
4.1 Magnetic pull-off instruments are mechanical instru- ments that measure the force required to pull a permanent magnet from magnetic material. The magnetic force of attrac- tion to the magnetic coating or coating-substrate combination is opposed by a spring or coil. Tension is applied to the spring/coil until the magnetic attraction to the material is overcome. The instrument must be placed directly on the coated surface to obtain a measurement. The force holding the permanent magnet to the magnetic material is inversely pro- portional to the thickness of the coating layer(s) between the magnet and the magnetic material. For example, a thin nickel layer applied to a nonmagnetic substrate will require less spring tension to pull the magnet off than will a thicker nickel layer, since the thinner coating has weaker magnetic strength.
4.2 Electronic instruments measure a change in magnetic flux density within the probe to produce a coating thickness measurement. The instrument probe must be placed directly (in a perpendicular position) on the coated surface to obtain a measurement. These instruments determine the effect on the magnetic field generated by the probe due to the proximity to the substrate.
8.1 Coating Thickness—Inherent in the method is a measur- ing uncertainty that, for thin coatings, is constant and indepen- dent ofthe coating thickness; for thicknesses greater than about 50 µm (2 mils), this uncertainty is proportional to the coating thickness.
8.2 Magnetic Properties ofthe Basis Metal (Type A coatings only)—Magnetic thickness measurements are affected by variations in the magnetic properties of the basis metal. For practical purposes, magnetic variations in low-carbon steel can often be considered to be insignificant. To avoid the influences of severe or localized heat treatments and cold working, the instrument should be adjusted using a reference standard having a basis metal with the same magnetic properties as that of the test specimen or, preferably and if available, with a sample ofthe part to be tested before application ofthe coating.
8.3 Basis Metal Thickness (Type A coatings only)—For each instrument, there is a critical thickness ofthe basis metal above which the measurements will not be affected by an increase in that thickness. Since it depends on the instrument probe (Note 1) and the nature of the basis metal, its value should be determined experimentally, if it is not supplied by the manu- facturer. N OTE 1—The term “instrument probe” also includes the term “magnet.”
8.4 Edge Effect—The method is sensitive to abrupt changes in the surface contour of the test specimen. Therefore, mea- surements made too near an edge or inside corner will not be valid, unless the instrument is specially adjusted for such a measurement. This also applies to measurements made on geometrically limited areas, such as narrow conductors on printed circuit boards.