Coating Inspection and Quality Assurance
The QA Mindset
At Level 3 you are expected to reason about the inspection system, not just execute individual tests. Understand the hierarchy: project specification and referenced standards govern; the inspector verifies conformance and documents it; the contractor controls execution. Know that inspection frequency, hold points, and acceptance criteria come from the specification, while test methods come from referenced standards (e.g., SSPC-PA 2 for dry film thickness, SSPC-SP 1 for solvent cleaning, ISO 8501-1 for visual surface preparation grades).
Environmental and Surface Checks
Track dew point, surface temperature, and relative humidity; the common rule is that steel must be at least 3 °C (5 °F) above dew point. Traps: confusing air temperature with surface temperature; assuming a hygrometer reading is the surface condition; forgetting that surface temperature can fall below air temperature after sunset or over thermal bridges.
DFT and Coverage
SSPC-PA 2 uses a 5-measurement spot average, with no individual reading below 80% of spec and the spot average at or above spec. Traps: averaging across a whole area instead of per spot; counting a low reading as acceptable because the average passes.
Documentation and Nonconformance
Records must be contemporaneous, legible, attributable, and traceable to location and batch. When a nonconformance is found, the inspector documents and reports; the inspector does not direct the contractor's workforce or waive specification requirements.
Worked Example
Spec: 8 mils DFT minimum. Five readings: 7.0, 7.2, 8.5, 9.0, 9.3. Spot average = 8.2 (passes ≥8.0), but 7.0 is below 6.4 (80% of 8.0)? 7.0 exceeds 6.4, so it passes. If a reading were 6.0, the spot fails despite a passing average.
Rule of Thumb
Every test result needs three things: the method, the location, and the acceptance criterion it was compared against.