Standard · Application and film thickness
ASTM D7091
Non-destructive DFT measurement with magnetic and eddy-current gauges.
ASTM D7091 covers how to use dry film thickness gauges. These are magnetic gauges for non-magnetic coatings on ferrous metals, and eddy-current gauges for non-conductive coatings on non-ferrous metals.
Three different words
- Calibration: done by the manufacturer or a qualified laboratory, with a certificate.
- Verification of accuracy: done by the user with reference standards, at least at the start and end of each shift.
- Adjustment: aligning the gauge reading to a known thickness, for example with shims on the surface to be coated.
Verification in practice
- If a gauge fails its check, treat every reading since the last good check as suspect.
- A Type 1 (magnetic pull-off) gauge is verified on certified coated plates, not on plastic shims. Shims suit Type 2 (electronic) gauges.
- On blasted steel, SSPC-PA 2 Appendix 8 adjusts a Type 2 gauge on the blasted surface or a blasted panel of similar steel, at one point or at two.
How many readings to take and how to accept them comes from SSPC-PA 2 or the specification.
7 practice items in the members area mention ASTM D7091 (CIP 1: 4 · CIP 2: 3).
Related
Try it in an exam-style question. The free readiness check shows the question style, explains every answer and gives you a dated study plan.
Take the free readiness checkSee the tracksAbout this page
This page describes the subject of ASTM D7091 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.