Dry film thickness (DFT)
The thickness of a coating after it has cured, measured in micrometres. It is a property of the specified system rather than a count of coats, and whether a job conforms to it is itself a measurement procedure — SSPC-PA 2 sets out how many readings, taken where, and what counts as conformance.
Dry film thickness is where a specification becomes checkable. A data sheet states a range for each coat and a total for the system, and the range has two bounds that both matter: below the minimum the barrier is incomplete, above the maximum the film traps solvent, cracks under thermal movement and fails early at edges.
Two coats that reach the specified thickness outperform three thin ones that do not. The number of passes is a means, never the requirement.
Sources and references
- StandardSSPC-PA 2-2022 — Procedure for Determining Conformance to Dry Coating Thickness RequirementsAMPP · accessed August 29, 2026
- StandardISO 12944-5:2019 — Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 5: Protective paint systemsInternational Organization for Standardization · accessed August 29, 2026
Where this is covered in depth
- How to Read an Industrial Coating Technical Data Sheet (TDS)Stop getting fooled by marketing claims. Learn the 8 critical points to check on any industrial coating Technical Data Sheet (TDS) before you specify it.
- Anti corrosion coating types: choosing by exposure zoneFive coating families, and the order that picks between them: corrosivity category first, durability class second, product last.