A dry surface is convenient for handling, but it does not necessarily show that an internal coating has reached its required chemical cure or released relevant residuals. Oil contact adds another compatibility boundary. The endpoint must be defined by the exact coating system. [1]
Use separate evidence gates
| Gate | Evidence | What it does not prove |
|---|---|---|
| Surface handling state | Specified dry-to-touch or handling check | Complete chemical cure |
| Cure condition | System-specific time/temperature and verification | Compatibility with every insulating liquid |
| Residual behavior | Qualified assessment of relevant solvent/extractable material | Absence from unsampled shielded regions |
| Oil contact | Coating and liquid property retention under representative exposure | Universal service life |
Match the tank history to the product requirement
Record coat thickness, application and cure temperatures, ventilation where relevant and any repair areas. A thick pocket or recently repaired weld region can differ from the main panel. Use the approved product criteria rather than extending one dry-time value to every film build.
Temperature outside the stated product basis needs an accepted interpretation. Do not invent an equivalent cure time from an average workshop reading or a generic reaction-rate rule.
Passing the cure gate does not establish oil compatibility. Evaluate the exact cured coating and insulating liquid as a material/liquid combination. [2]
Compare the coldest film with the approved cure record
Assume a product-specific validated cure requires 12 h after the film reaches 25 °C. The coldest repaired region reaches that temperature 3 h after the timer starts. At a 12 h timer end, only 9 h satisfies the assumed premise, leaving 3 h unresolved. Use actual product evidence rather than inventing a generic time-temperature equivalence.
References
- ISO, ISO 12944-7:2017, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 7: Execution and supervision of paint work.
- IEC, IEC 63177:2024, Test methods for compatibility of construction materials with electrical insulating liquids.