ASTM D7378-16 (2024) PDF

Full title and description

ASTM D7378-16(2024) — Standard Practice for Measurement of Thickness of Applied Coating Powders to Predict Cured Thickness. This practice describes procedures and portable instruments for measuring the thickness of dry, applied powder coatings in the pre-cured (pre-gelled) state to predict the cured film thickness and to help set up and control application systems.

Designation shown as D7378-16R24 indicating the 2016 practice as reaffirmed/updated in 2024.

Abstract

This standard practice provides three measurement procedures (rigid metal notched or "comb" gauges, magnetic/eddy-current powder probes, and non-contact ultrasonic powder thickness instruments) for assessing uncured powder thickness and deriving or applying reduction factors that predict cured thickness. It documents significance, advantages, limitations and recommended use of portable instruments for a variety of rigid substrates.

General information

• Status: Active (reaffirmed/updated 2024).
• Publication date: 2024 (D7378-16 with 2024 reissue/update noted).
• Publisher: ASTM International (Annual Book of ASTM, Volume 06.02).
• ICS / categories: Properties of surfaces / coating thickness (ICS code cited in listings: 17.040.20).
• Edition / version: D7378-16(2024) — original approval 2016, shown as D7378-16R24 on ASTM listings.
• Number of pages: 5 pages.

Scope

Describes measurement of dry (uncured, pre-gel) coating powder thickness on rigid substrates and provides three procedures: Procedure A — rigid metal notched (comb) gauges; Procedure B — magnetic or eddy-current coating thickness gauges with specialized powder probes; Procedure C — non-contact ultrasonic powder thickness instruments. The practice explains how to determine or apply a reduction factor to predict cured film thickness, notes limitations of each technique, and stresses following instrument manufacturers' instructions. It is intended for portable instrument use and does not replace instrument manufacturers' operating guidance.

Key topics and requirements

• Measurement of applied powder in the pre-cured (pre-gelled) state to predict cured film thickness.
• Procedure A — rigid metal notched (comb) gauges for direct visual/physical determination of powder height.
• Procedure B — magnetic or eddy-current gauges with powder probes (micro‑pins) that contact the powder to determine depth relative to the substrate.
• Procedure C — non-contact ultrasonic instruments that predict cured thickness from calibrations or typical powder profiles; adjustment/calibration recommended for non‑typical powders.
• Establishing and applying a reduction factor (ratio of cured thickness to uncured measurement) where required to improve prediction accuracy.
• Notes on advantages, limitations, and the need to follow safety and instrument manufacturer instructions; SI units are the standard.

Typical use and users

Used by powder coating applicators, quality control and inspection laboratories, coating formulators and manufacturers, OEM production engineers, and instrument suppliers for process setup, in-line checks, and quality assurance to avoid over- or under-application and to predict cured film properties. Portable gauges and handheld ultrasonic/eddy-current instruments commonly used in production settings reference this practice.

Related standards

References to other ASTM methods and practices for coating thickness measurement and cross‑sectioning appear in the practice, including Practice D7091 for magnetic/eddy-current coating thickness measurement over metals, Test Method D6132 for ultrasonic thickness measurement over non-metal substrates, and Practice D4138 for destructive cross‑sectioning techniques.

Keywords

powder coating, coating powder, powder thickness, film thickness, cured thickness prediction, comb gauge, powder probe, ultrasonic powder gauge, magnetic/eddy-current, reduction factor.

FAQ

Q: What is this standard?

A: ASTM D7378-16(2024) is a standard practice that specifies procedures for measuring the thickness of applied powder coatings in the uncured state to predict the cured film thickness and support process control and quality assurance.

Q: What does it cover?

A: It covers three procedures (comb/ notched gauges; magnetic/eddy-current powder probes; and non-contact ultrasonic instruments), guidance on establishing reduction factors to predict cured thickness, instrument limitations, and general significance and use.

Q: Who typically uses it?

A: Production and process engineers, QC/inspection labs, coating and powder manufacturers, applicators, and instrumentation suppliers use the practice for setup, verification and in-process monitoring of powder coating applications.

Q: Is it current or superseded?

A: The practice is active and shown as D7378-16 with a 2024 reissue/update (listed as D7378-16R24 / D7378-16(2024) in ASTM catalogs). Users should refer to the ASTM catalog entry for the most recent status and revision history.

Q: Is it part of a series?

A: It is part of ASTM's coatings and surface properties collection (Book of Standards Volume 06.02) and was developed by Subcommittee D01.51; it cross-references related ASTM methods for cured-film thickness and cross-sectioning.

Q: What are the key keywords?

A: powder coating, film thickness, powder thickness measurement, cured thickness prediction, comb gauge, ultrasonic powder gauge, eddy-current powder probe.