title = "Coating Adhesion Testing Methods"

content = """
Adhesion testing verifies that a coating is properly bonded to its substrate and will perform as intended in service. At Ridgecrest Metalworks, adhesion testing is carried out on production witness panels, on coated parts after process changes, and as part of periodic process audits.

Cross-cut adhesion test (ISO 2409 / ASTM D3359 Method B) is the most common in-process adhesion check for paint and powder coat on metal. A cross-hatch grid of cuts is made through the coating to the substrate using a calibrated cross-cut tool (blade spacing 1 mm for thin coatings, 2 mm for coatings 60–120 µm, 3 mm for thicker coatings). Adhesive tape (specified tack level) is applied over the grid, pressed firmly, and then pulled off rapidly at 180 degrees. The result is rated 0–5 based on the percentage of coating removed: 0 = no removal (best), 5 = > 65 % removal (fail). Acceptance criterion at Ridgecrest is typically rating 0 or 1.

Pull-off adhesion test (ISO 4624 / ASTM D4541) measures the tensile force required to detach a coating from the substrate. A dolly (cylindrical metal disc) is bonded to the coated surface using a two-part adhesive. After adhesive cure, a pull-off tester (hydraulic or pneumatic, hand-operated or automatic) applies a perpendicular tensile load. The result is expressed in MPa or psi. The failure mode (adhesive, cohesive, or inter-coat) is as important as the strength value. Minimum pass values are defined per coating system; typical primer-to-substrate values should exceed 5 MPa for epoxy primers.

Wedge-bend test (ASTM D522) evaluates coating flexibility and adhesion simultaneously by bending a coated metal panel over a conical mandrel. Cracks or detachment of the coating near the bend indicate poor adhesion or insufficient flexibility.

Tape test for zinc-rich primers (ASTM D6677) applies tape after the primer has cured and checks for lifting. Zinc-rich primers that are over-applied or insufficiently cured fail this test by cohesive fracture within the zinc-rich layer.

Adhesion test panels are produced at the start of each production run (or daily for continuous lines) and retained with the batch record. Test panels use the same substrate material (type and surface preparation) as production parts. Results are recorded in the quality log, and any failure triggers stop-production and investigation before parts are processed or released.
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version = "0.0.1"
