ASTM E376 is an ASTM International standard practice that outlines nondestructive procedures for measuring coating thickness on electrically conductive metal substrates using magnetic-field and eddy current instruments.

What is the difference between the magnetic method and the eddy current method in ASTM E376?

The magnetic method is used for nonmagnetic coatings on magnetic substrates, such as paint on steel. The eddy current method is used for nonconductive coatings on nonmagnetic conductive substrates, such as paint on aluminum.

Why is calibration important under ASTM E376?

The page states that regular calibration against known standards is essential because measurement accuracy is affected by instrument setup, surface roughness, curvature, cleanliness, magnetic permeability, and electrical conductivity.

What accuracy does ASTM E376 describe?

Under ideal conditions, the page states that measurement accuracy can be within plus or minus 10 percent of the actual coating thickness or plus or minus 2.5 micrometers (0.0001 inch), whichever is greater.

Which industries commonly use ASTM E376?

The page identifies aerospace and defense, automotive manufacturing, marine and shipbuilding, electronics manufacturing, and construction and infrastructure as key industries using ASTM E376.

What are the benefits of working with an ASTM E376 provider?

The page highlights nondestructive testing, versatility across substrate and coating combinations, alignment with ISO 2178 requirements, and stronger quality assurance for coating thickness compliance and durability.

Armoloy Specifications

ASTM E376

Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy Current (Electromagnetic) Testing Methods

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Armoloy Specifications

What is ASTM E376?

ASTM E376 is a standardized practice developed by ASTM International that outlines procedures for nondestructive measurement of coating thickness on electrically conductive metal substrates using magnetic-field and eddy current instruments. This practice is applicable to both ferrous and nonferrous substrates and can measure coatings that are either electrically conductive or insulating.

The standard ensures accurate and reliable thickness measurements, which are critical for assessing coating performance, corrosion protection, and adherence to engineering specifications.

electromagnetic test for coating thickness per ASTM E376 standard

Purpose and Applications of ASTM E376

ASTM E376 serves as a guideline for selecting and using appropriate instruments to measure coating thickness without damaging the part. It is particularly useful in industries where precise coating measurements are essential for quality control and performance, including:

Aerospace and Defense: Ensuring protective coatings meet stringent specifications.
Automotive Manufacturing: Verifying paint and plating thickness for durability and aesthetics.
Marine and Shipbuilding: Assessing corrosion-resistant coatings on hulls and components.
Electronics: Measuring thin conductive or insulating layers on components.
Construction: Evaluating protective coatings on structural steel.

Inspector performing eddy current testing on heat exchanger tubes for pitting corrosion and loss of coating thickness

ASTM E376 Testing Methodology

Magnetic Method

Magnetic-type gauges operate based on the magnetic attraction between a magnet and the substrate or the reluctance of a magnetic flux path through the coating and substrate. These gauges are designed to measure the thickness of nonmagnetic coatings on magnetic substrates (e.g., paint on steel).

Eddy Current Method

Eddy current-type gauges are electronic instruments that measure variations in impedance caused by coating thickness variations. They are suitable for measuring nonconductive coatings on nonmagnetic, conductive substrates (e.g., paint on aluminum).

Accuracy and Calibration

The accuracy of measurements depends on several factors:

Instrument Calibration: Regular calibration against known standards is essential.
Surface Conditions: Surface roughness, curvature, and cleanliness can affect readings.
Material Properties: Variations in magnetic permeability and electrical conductivity of the substrate and coating.

Under ideal conditions, the measurement accuracy can be within ±10% of the actual coating thickness or ±2.5 µm (±0.0001 in.), whichever is greater.

astm and ams values around magnifying glass

Industries that Follow ASTM E376

Aerospace & Defense: For verifying coating thickness on aircraft components and military equipment.
Automotive Industry: Ensuring uniform paint and plating thickness on vehicles.
Marine Industry: Assessing protective coatings on ships and offshore structures.
Electronics Manufacturing: Measuring thin films and coatings on electronic devices.
Construction and Infrastructure: Evaluating protective coatings on bridges, buildings, and pipelines.

Benefits of Working with an ASTM E376 Provider

Nondestructive testing

Allows for coating thickness measurement without damaging the part

Versatility

Applicable to a wide range of substrate and coating combinations

Compliance with international standards

Aligns with ISO 2178 requirements

Quality assurance

Ensures coatings meet specified thickness requirements for performance and durability

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Disclaimer

The information provided on this page, including any descriptions, interpretations, or summaries related to ASTM E376, is offered solely by The Armoloy Corporation for general informational purposes. This content reflects Armoloy’s internal understanding and practical application of ASTM E376 within its own processes and does not constitute official or authorized guidance from ASTM International.

ASTM E376 is a proprietary standard developed and owned by ASTM International. Armoloy makes no claim to ownership of this specification and does not reproduce, quote, or distribute any protected content from the original document. References to ASTM E376 are made in accordance with fair use principles and are intended to illustrate Armoloy’s alignment with widely recognized infrared temperature measurement practices.

This content is not intended to substitute for the official specification, which should be obtained directly from ASTM International. Readers are strongly encouraged to consult the original standard and qualified professionals for definitive technical or compliance information.

The Armoloy Corporation makes no warranties, express or implied, regarding the accuracy, completeness, or applicability of this content and disclaims all liability for any reliance placed upon it. This disclaimer is subject to change without notice and does not create any contractual relationship or obligation.