Coating Inspection
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Submerged Coatings DFT Inspection
Submerged Coatings DFT Inspection
Coating: Modified Polyamine Epoxy
Application: Submerged service; wastewater treatment plant clarifiers
Currently inspecting new submerged coating (Tnemec 66 and 141) for dry film thickness. Specification calls for 4-6 mils primer and 10-15 mils top coat. So total DFT requirement is 14-21 mils. Some of the coating is applied to the inside and outside of a 10 ft diameter drum (open on top and bottom). The remainder is applied to angle iron fabricated into a truss like structure 80 ft long.
There is no spec for testing DFT’s other than the implication that any DFT reading cannot be less than 14 mils which is probably unreasonable. However, applying SSPC PA2 (5 avg readings over 100 sq ft) to the drum seems inadequate to me for submerged coatings and since we’ve had quality control problems with the painter. Any advice on how to tighten up PA2 to catch areas of low DFT’s?
Also, PA2 doesn’t seem practical when testing small surface areas (such as angle iron). I’ve proposed taking 4 or 5 readings for each length along each face of each angle (generally 6-8 ft) and averaging that. Any thoughts?
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