ASTM D2247 Water Resistance of Coatings in 100% Relative Humidity
In ASTM D2247, coated specimens are placed in a chamber at 38 °C with a saturated atmosphere, so water droplets keep forming on the coating surface. The test simulates film damage similar to that caused by continuous condensation in service conditions. This test finds adhesion losses and blisters that are not found in a salt spray run. MatX Lab conducts the test on painted metals, powder coatings, e-coat, and coated composites, following ASTM D2247.
What Is ASTM D2247?
ASTM D2247 is the standard practice for testing the water resistance of coatings in 100% relative humidity. Specimens sit in a chamber where heated water below the specimen zone keeps the air saturated. Because the specimens run slightly cooler than the vapor, water condenses on them and keeps condensing for as long as the exposure lasts.
The chamber holds 38 °C. The test uses no salt, acid, or ultraviolet light, which is the point: whatever damage appears comes from water and temperature alone. Failure shows up as blistering, film softening, loss of adhesion, color change, or corrosion creeping out of a scribe. Each of those has its own rating standard, and the practice itself measures none of them.
ASTM D2247 Scope and Applications
The test is conducted on organic and/or inorganic coatings applied to substrates that can withstand a saturated atmosphere at 38 °C. Generally, steel and aluminum panels have been used; however, coated composites and plated articles are sometimes tested.
Applications:
- Adhesion testing. Identifying coating systems that are susceptible to debonding from the substrate when exposed to water at the interface level, which is the most frequent problem detected by this test.
- Verification of pretreatment system. Making sure that a phosphating, chromating, or silanizing system works properly prior to applying any coating.
- Specified performance testing. Achieving a specified time frame without blistering higher than a specified grade.
- Formulation evaluation. Evaluating binders, pigmentation, and film thickness under equivalent wet conditions.
The salt spray test follows ASTM B117, while the cyclical or acidified version follows ASTM G85. Exposure tests that involve sunlight and water should follow the xenon arc exposure test, ASTM D7869. The condensation and daily dry test follow a completely different approach, so please let us know which failure mode you would like to test.
ASTM D2247 Test Procedure
The practice is simple to run and easy to get wrong. Most errors trace back to specimen preparation and to what happens in the first hour after removal.
| Step | What happens |
| Specimen preparation | Panels are identified, film thickness is measured, and cut edges and backs are sealed where the specification requires it. |
| Baseline record | Gloss, color, and film thickness are recorded before exposure, so post-exposure change is measurable rather than remembered. |
| Scribing | A scribe through to the substrate is cut when creep from a coating defect is under study. |
| Chamber loading | Specimens are supported so condensate runs off freely, with no specimen dripping onto another and no contact between faces. |
| Conditioning | The chamber stabilizes at 38 °C with the atmosphere saturated and visible condensate forming on the specimen surfaces. |
| Exposure | The exposure runs continuously. Inspection openings are logged, and specimens return in the same position and orientation. |
| Removal | Specimens come out at the agreed duration and get examined immediately, since softened films recover within minutes and blisters can collapse. |
| Rating | Blistering is graded under ASTM D714, rust under ASTM D610, adhesion under ASTM D3359, and gloss retention under ASTM D523. |
Limitations: This procedure doesn’t address salt spray testing, UV exposure, or thermal cycling, and a coating that can stand 1000 hours in this procedure can fail after one season when exposed outside. The time of sample removal will define whether the adhesion test is positive or negative, since the film that is soft and swollen during removal will show failure in 30 minutes and pass in 24 hours. Decide on the inspection time beforehand and use the same inspection time for all specimens. Unsealed specimen edges will corrode first and affect the overall coating evaluation.
ASTM D2247 Specimen Requirements and Test Conditions
| Parameter | Typical requirement |
| Panel dimensions | 75 mm x 150 mm standard, up to 100 mm x 300 mm within rack capacity |
| Replicates | Three per condition minimum |
| Film thickness | Measured and reported per panel, since blister resistance tracks it |
| Edge treatment | Cut edges and reverse faces sealed unless you instruct otherwise |
| Chamber temperature | 38 °C, held within 1 °C |
| Humidity | Saturated, with condensate visible on specimens throughout |
| Duration | Set by specification, commonly 24, 96, 240, 500, or 1000 hours |
Send panels coated the way your product is coated. A hand-drawn film on a lab panel and a production-line finish behave differently under condensation, and the exposure will find that difference before your customer does.
Nominate the inspection points at quotation. Adding a 500-hour interim check to a 1000-hour run costs nothing if we plan it, and we can’t add it afterward.
ASTM D2247 Test Results and Reporting
The D2247 report includes the exposure period, the conditions recorded in the chamber during the test, and the status of each panel during inspections. We evaluate the panels’ performance according to the rating systems described in the following standards: ASTM D714 for blister ratings, ASTM D610 for rust ratings, ASTM D3359 for adhesion ratings, and ASTM D523 for gloss before and after the test. Photographs of each panel after its removal are included.
If the controls were tested along with your panels, the results are provided in the table. The time elapsed from removal to the adhesion test is also provided in your report, since it affects the results.
ASTM D2247 FAQs
How is the test different from a salt spray test?
ASTM D2247 uses pure condensing water without any salt. It is meant to detect failures resulting from water penetration. ASTM B117 introduces chloride and initiates corrosion in defects.
Can you expose parts instead of panels?
Yes, within rack capacity, provided condensate can run off rather than pool. Parts that trap water in recesses produce results that flat panels will not reproduce.