Investigators: Carlos R. Beauchamp, Hilary B. Gates, David R. Kelly, and Jasper L. Mullen

Technical Description:

These standards consist of pre-configured sets of coupons of fine grained copper with thickness ranging from 2.5 µm to 2 mm, that has been electrodeposited onto low carbon steel substrates. The uniform coatings are then overplated with a thin protective layer of chromium and the coupon's total coating thickness is then certified. They are primarily intended for use in calibrating coating thickness measurement instruments based on the magnetic induction principle and are used by the organic and inorganic coating industry for the non-destructive measurement of non-magnetic coatings over magnetic substrates.

Technical Objectives:

• Total re-evaluation of the production and certification of the Coating Thickness Calibration Standards to accommodate advances made on the precision of the instruments employed in the laboratory and in the field.

• Bring the project in compliance with the present policy for reporting uncertainties associated with measurements executed at NIST.

• Manufacture and certification of replacement Primary Calibration Standards employed in the production process.

Anticipated Outcome:

• Increased efficiency during the production and certification stages of the Standard Reference Materials (SRM).

• Reduced uncertainties due to changes made in the fabrication and certification stages of the standard.

• Replacement of the Primary Standards used during the certification process.

Accomplishments for FY 1995:

• The effects of thickness, composition, surface roughness and mechanical working of the substrate material on the uncertainties associated with the thickness measurement have been evaluated during the material selection for the production of these standards.

• Stricter control over the cell geometry and electrode configuration during the electrodeposition stages now yield uniform standards with less than 1% deviation from the average thickness values.

• Proper match of probe sensitivity to the thickness measured, increased resolution during probe positioning, coupled with the elimination of false triggering, reduced degrees of freedom during human operations, and a different mathematical model to fit the probe responses during the calibration modes have reduced the uncertainties of the certification process.

• The Primary Standards have been fabricated and await the certification of their thickness.

Impacts and Technical Highlights:

• The first major revision of the Coating Thickness Calibration Standards SRM's 1357 through 1364a nears its completion and is expected to reach customers before the fiscal year 1996 is over and remaining stock of previous standards is consumed.

• Uncertainties associated with the standard have been minimized allowing greater leeway during the selection of the measurement spot by the end user.

• To better serve the customers of the standard, the thickness distrubution offered within the pre-configured sets is being tailored in response to a survey presented to the users of the standard, inquiring about the thickness ranges of their present applications and the uncertainties associated with their measurement protocol.

Back to Table of Contents

Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister