The NIST SRMs 1358 to 1364 are employed in the calibration of the instrumentation used to measure non-magnetic coatings over magnetic substrates (and vice versa) based on magnetic principles. These SRMs range in thickness from 6 μm to 2 mm and are sold directly to end users.
The NIST Coating Thickness SRMs are standards that offer traceability to a National Measurement Institute (NMI) for the calibration of coating thickness gauges that employ magnetic principles. The Thin Film and Nanostructure Processing Group also provides verification services in support of the standards produced.
The SRMs consist of an AISI 1010 cold rolled sheet steel substrate with a uniform electrodeposited coating of copper that is overplated with a thin protective layer of chromium. Each coupon is individually certified for total coating thickness. The units are packaged as sets and are comprised of five 45 mm × 45 mm coupons: a bare substrate plus four additional thicknesses of coatings.
Customers of these SRMs are the industries that presently require traceability to an NMI, including the nuclear power industry, the transportation sector (railway and steel bridge maintenance), and the military. In addition, other customers presently purchasing these standards come from the broader surface finishing industry (automotive, home appliance, other decorative finishing).
In 1999, the program went through its last revision in which uncertainties were lowered from 5% to a maximum of 2% of the certified coating thickness, but the intent of selling directly to the end users was kept. Presently, in addition to satisfying the demand for these standards, the Group is involved in the production of a new series of standards targeting the secondary standard producers, with an assigned maximum uncertainty of 1% of the certified coating thickness. These standards will enable secondary standard producers to demonstrate traceability to an NMI, while replacing NIST as a direct-to-customer supplier.
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