Standard Practice for Testing Coatings’ Water Resistance as per ASTM D1735

What Is ASTM D1735?

ASTM D1735 is the Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus, published by ASTM International. The standard describes a procedure for evaluating the resistance of coatings to the effects of water condensation by exposing coated test specimens to a high-humidity fog environment in a controlled test chamber.

Unlike salt spray tests that assess corrosion resistance in saline environments, ASTM D1735 specifically evaluates the response of organic coatings to pure water vapour condensation — simulating conditions such as morning dew, high-humidity industrial environments, and condensation in poorly ventilated enclosures.

Scope and Purpose of ASTM D1735

The test applies to a wide range of organic coatings, including architectural paints, industrial maintenance coatings, automotive topcoats, wood finishes, and anti-corrosion primers. It is used to:

• Assess coating susceptibility to blistering, softening, loss of adhesion, and colour change under humid conditions
• Compare the water resistance performance of different coating formulations
• Screen new formulations before more extensive outdoor or accelerated weathering testing
• Verify compliance with product specifications and OEM coating approval requirements

Test Equipment: Water Fog Apparatus

The water fog apparatus (sometimes called a humidity cabinet) maintains the test chamber at a temperature of 38°C ± 1°C (100°F ± 2°F) with near 100% relative humidity achieved by a fog of distilled or deionised water. The condensation formed continuously wets the exposed coating surfaces.

Test panel holders position specimens at an angle (typically 15° from vertical) to allow condensate to drain while maintaining continuous film wetness. Test duration ranges from 24 hours to several hundred hours, depending on the application standard.

Evaluation Criteria After ASTM D1735 Exposure

After exposure, test panels are evaluated for:

• Blistering: Assessed per ASTM D714 using a standardised frequency and size rating scale
• Softening: Pencil hardness or thumb-pressure assessment compared to unexposed control
• Loss of Adhesion: Cross-cut adhesion per ASTM D3359
• Colour and Gloss Change: Colorimetric and gloss measurements compared to pre-exposure values
• Corrosion at Scribe: For anti-corrosion coatings, scribes are assessed for rust creep and undercutting per ASTM D1654

Difference Between ASTM D1735, D2247, and D4585

ASTM D1735 uses a water fog spray for film wetting, ASTM D2247 uses 100% relative humidity without direct fog spray (pure condensation), and ASTM D4585 uses controlled condensation at elevated temperature. These subtle differences influence which failure modes are most readily accelerated and which are most representative of specific end-use environments.

Industrial Applications

Architectural coating manufacturers use ASTM D1735 as a routine quality screen for exterior paints. Industrial coating suppliers use it to qualify protective coatings for marine, offshore, and water infrastructure applications. Automotive OEMs require ASTM D1735 or equivalent tests as part of coating system approval packages.

Conclusion

ASTM D1735 is a widely used standard for evaluating the water resistance of coatings under high-humidity, condensation-rich environments. Simulating real-world exposure conditions, such as dew formation and persistent moisture, helps identify coating weaknesses like blistering, adhesion loss, and surface degradation. As part of a broader coating qualification framework, testing to ASTM International ASTM D1735 provides valuable insights for formulation development, quality control, and long-term performance assessment in moisture-prone environments.

Why Choose Infinita Lab for ASTM D1735 Coating Water Resistance Testing?

Infinita Lab offers ASTM D1735 water fog testing alongside complementary coating evaluation services, including salt spray (ASTM B117), humidity (ASTM D2247), and adhesion testing through our nationwide network of accredited laboratories.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.

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