Category: Finishes
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Dry film thickness is the thickness of paint once dry, measured in microns with a gauge, and set for each coat of the paint system.
Why it matters on a project
Too thin shortens corrosion protection; too thick can crack. Measurement is the only proof the work matches the specification.
Measurement and pricing
Multiple readings per area are recorded in the inspection report.
Worked example
A three-coat system: primer 75 + intermediate 125 + finish 75 microns = 275 microns total dry film thickness.
Common mistake
Measuring only a few easy-to-reach spots and leaving edges and corners unchecked.
Frequently asked questions
What is the difference between wet and dry film thickness?
Wet is measured while applying, dry after curing; the ratio depends on the paint's solids content.
How many readings per area?
The specification or reference standard sets them, with extra readings at edges and corners.
Related terms
- Surface preparationCleaning a steel surface to a specified grade (e.g. SSPC-SP 10) before coating to ensure adhesion.
- Steel structureA structural frame of steel sections connected by welding or bolts, protected from corrosion by coating.
- Quality control planThe list of inspections, tests and hold points for each activity and who approves them.
- Inspection request (IR)A formal request from the contractor to the consultant to inspect work before the next stage.
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