“Measurement of Dry Coating Thickness with magnetic Gages”
HOW MUCH IS ENOUGH?
Statistical method to determine the minimum number of readings required.
SSPC-PA 2 – Measurement of Dry Paint Thickness with Magnetic Gauges
- Procedures to Measure Dry Film Thickness of Nonmagnetic Coatings over Magnetic Substrates
–Type 1 – Magnetic Pull-Off
–Type 2 – Fixed Probe
- Calibration – Type 1
–Verify accuracy on NIST plates
–Measure (A) several points on bare, prepared substrate
–Measure (B) the dry film
–Subtract (A) from (B) to obtain dry film thickness
- Calibration – Type 2
–Verify accuracy on nonmagnetic shims over the bare, prepared substrate
- For Structures not exceeding 300 sq ft, take 5 spot readings per 100 sq ft
- For Structures not exceeding 1000 sq ft, Select 3 random 100 sq ft areas to test
- For Structures exceeding 1000 sq ft, Select 3 random 100 sq ft areas to test in the first 1000 sq ft and for each additional 1000 sq ft test one random 100 sq ft area.
- If any area is not in compliance, the non compliant area should be determined.