ASTM D1735-21 PDF

Overview

ASTM D1735-21: Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus is a widely adopted international standard published by ASTM International. This standard outlines the procedures and essential principles for evaluating the water resistance of coatings and coatings systems using a water fog (mist) environment, similar to apparatus used for salt spray testing. Understanding a coating's resistance to water exposure is crucial for predicting its service life and ensuring performance in real-world environmental conditions.

By assessing coatings under controlled water fog exposure, ASTM D1735-21 provides valuable data for manufacturers, formulators, and researchers seeking to verify or improve the durability and reliability of painted or coated surfaces.

Key Topics

• Water Fog Test Methodology: Describes the process for exposing coated specimens in a controlled water fog chamber, maintaining a standard temperature (typically around 38°C or 100°F), and specifying duration based on product and customer requirements.
• Performance Evaluation: Outlines how effects such as color change, blistering, loss of adhesion, softening, or embrittlement should be observed and recorded after exposure to water fog, both immediately and after a recovery period.
• Pass/Fail Criteria: Defines that a coating system passes the water fog test if there is no evidence of water-induced failure after the specified test period. Partial or complete failures are documented for further analysis.
• Test Controls and Documentation: Emphasizes the importance of using control specimens, ensuring proper specimen orientation and spacing, and rotating specimens to minimize apparatus variability and ensure reliable results.
• Equipment Specification: Specifies use of an apparatus similar to ASTM B117 (salt spray), with detailed guidelines for fog collection rates, chamber temperature monitoring, and annual mapping of fog collection within the test area.
• Reporting Requirements: Provides a checklist for reporting results, including identification, evaluation outcomes, test conditions, fog collection rates, and specimen mounting details.

Applications

The ASTM D1735-21 water fog test is applied across various industries to ensure coatings meet performance requirements before being used in service environments where moisture exposure is a concern. Common applications include:

• Paint and Coating Formulation: R&D of new coating systems with improved moisture resistance for automotive, aerospace, marine, and architectural uses.
• Quality Control: Routine inspection and verification of batch-to-batch consistency in coating manufacturing.
• Specification Compliance: Demonstrating that coatings meet contractual or regulatory standards for water resistance during procurement or product certification.
• Substrate Surface Treatment: Evaluating substrate preparation methods and their interaction with coatings for optimal durability.
• Comparative Testing: Comparing the water resistance of different coating formulations or surface treatments for product selection and optimization.

It is important to note that results from the water fog test should not be directly equated to natural weathering performance unless supported by correlation studies.

Related Standards

For comprehensive assessment of coatings and related products, ASTM D1735-21 references and complements several related standards:

• ASTM B117 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• ASTM D870 - Water Resistance of Coatings Using Water Immersion
• ASTM D2247 - Water Resistance of Coatings in 100% Relative Humidity
• ASTM D4585 - Water Resistance of Coatings Using Controlled Condensation
• ASTM D610 - Evaluating Degree of Rusting on Painted Steel Surfaces
• ASTM D714 - Evaluating Degree of Blistering of Paints
• ASTM D609, D823, D1730 - Preparation and Application of Panels and Films

These related standards provide additional procedures and context for holistic evaluation of coating systems under various environmental stresses, supporting robust product development and qualification processes.

Keywords: ASTM D1735-21, water fog test, water resistance, protective coatings, paint durability, accelerated testing, coating evaluation, quality control, ASTM standards.