The test works by dropping a standard weight from varying heights to deform the coating and its underlying substrate. It identifies the precise point at which the coating fails, establishing an "impact value" measured in inch-pounds (in-lb) or Joule-meters (J). Direct vs. Reverse Impact The standard outlines two distinct types of impact testing:
Developed by ASTM International (formerly the American Society for Testing and Materials), this standard describes a procedure for rapidly deforming a coated panel and evaluating the coating's ability to resist cracking or detachment from the substrate.
Raise the weight to a specific height on the graduated tube and release it. The weight strikes the indenter, driving it into the panel to create a deformation. 5. Evaluating Failure
The industry benchmark for this assessment is . This standard provides a highly repeatable laboratory procedure for estimating the resistance of organic coatings to the impacts of rapid deformation. What is ASTM D2794?
Optional chemical or electrical testing tools used to identify hairline fractures in the coating that are invisible to the naked eye. 4. Step-by-Step Testing Procedure astm d2794 pdf
The standard is formally titled: "Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)."
The weight strikes the uncoated reverse side of the panel, causing a convex deformation on the coated side. Test Equipment and Components
While the standard provides a solid foundation, the official ASTM D2794 PDF document notes that this test method should be primarily restricted to testing within because of the poor reproducibility of the method between different labs. For consistency, it is highly recommended to: Use the same operator for testing. Use the same, calibrated equipment.
Performing the test correctly is critical for reliable results: The test works by dropping a standard weight
Access to the official PDF is essential for several reasons:
A graduated tube (typically 24 to 48 inches long) that guides a falling weight. It features markings in inch-pounds or meter-kilograms to measure the distance of the drop accurately.
Coatings must be applied uniformly to flat, thin metal panels (usually steel or aluminium).
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If you're looking for a PDF version of the ASTM D2794 standard, here are a few options:
A cylindrical weight with a hemispherical head (tup). The head typically has a diameter of either 0.625 inches (15.9 mm) or 0.500 inches (12.7 mm).
While both measure impact resistance, ISO 6272 is the international equivalent standard. ISO 6272 introduces distinct variations in weight masses, falling distances, and metric units. It also splits the testing methods across two parts based on the area of the indenter. Can this test be performed on plastic substrates?