Inspection, Testing, and Quality Control
Inspection is planned, not improvised. Before work, review the inspection and test plan, hold points, specification, product data sheets, and calibration records. During preparation, verify cleanliness standard, profile, salt level, and surface defects. During application, record steel temperature, dew point, RH, product batch, thinner, and wet-film thickness. After cure, inspect visually for runs, sags, dry spray, holidays, and misses; then measure DFT with a calibrated gauge following SSPC-PA 2. A common trap is taking DFT readings without calibrating on a smooth plate of similar curvature or without enough readings per area. Another is treating a single low reading as acceptable because the average passes; the 80/20 rule normally requires the average to meet specification and no reading below 80% of the minimum. Holiday detection must use the correct voltage for the film thickness and substrate; too high a voltage can damage a sound film. Adhesion tests are destructive, so plan their locations and repair them. Worked example: spec DFT is 4.0–6.0 mil. Readings 3.4, 4.2, 4.6, 5.0, 5.8 mil: average 4.6 mil passes, minimum 3.4 mil is above 80% of 4.0 (3.2 mil), and maximum 5.8 mil is below 6.0, so the set passes. Rule: record the reading, the location, and the gauge identification.