ASTM D1735 Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus

    What is ASTM D1735? 

    ASTM D1735 is a standard practice that covers the basic principles and operating procedures for testing coating water resistance in an apparatus similar to that used for salt spray testing under Practice B117. This practice is limited to the methods of obtaining, measuring, and controlling the conditions and procedures of water fog tests. Laboratories using ASTM D1735 (Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus) place coated test specimens in a watertight cabinet where a continuous, indirect spray of demineralized water falls onto the specimens at a rate of 1.5 to 3.0 mL/80cm²/hour, maintaining a chamber temperature of 38°C (100°F) unless otherwise specified. This practice is performed in a demineralized water environment, unlike the salt spray environment described in Practice B117, and the same apparatus can be used to switch between the two test environments, provided technicians first remove all salt from the cabinet and reservoir. Engineers use this practice to estimate the useful life of protective coatings because water exposure causes coatings to deteriorate over time. 

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    Get Certified ASTM D1735 for Reliable Coating Water Resistance Verification 

    Certification confirms that the water resistance test meets the required ASTM D1735 water resistance testing conditions, such as fog deposition rate and chamber temperature. The ASTM D1735 test is used to determine how a coating performs when exposed to water fog before manufacturers accept it into the market for use in the architectural, industrial, automobile, or anti-corrosion market. The practice is used to verify conformance to ASTM D1735 requirements and to aid in the prediction of the service life of a coating. 

    What is the Scope of ASTM D1735? 

    ASTM D1735 is a standard practice that provides the general principles and procedures for water resistance testing using an apparatus similar to the salt spray testing. Measures the resistance to water penetration from a continuous fog of demineralized water in a controlled temperature chamber. This practice establishes a standard procedure for the generation and maintenance of a water fog test environment, and utilizes equipment compatible with the salt spray test in Practice B117.

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    ASTM D1735 is primarily designed to provide the conditions and procedures for the exposure of coatings in a controlled water fog environment. The technique is used in industry for the prediction of service life, formulation comparison, and quality control.

    The scope of ASTM D1735 includes 

    • Material type: Coated test specimens such as architectural, industrial, automotive, and anti-corrosion coatings. 
    • Purpose: To develop procedures for water fog acquisition, measurement, and control. 
    • Properties measured: Coating water resistance, measured by the degradation of coatings (such as loss of adhesion, blistering). 
    • Method: The method involves placing coated specimens in a watertight cabinet to be subjected to a constant fog of demineralized water at 38ºC (100ºF). 
    • Result: Related test methods are used for the evaluation of results, such as cross-cut adhesion loss after exposure (Test Method D3359). 
    • Test Limitations: This practice applies to the methods for obtaining, measuring, and controlling water fog test conditions, but it does not specify acceptance or failure criteria. 
    • Environmental conditions: The influence of the water resistance test is highly dependent on environmental conditions, such as temperature in the chamber and fog deposition rate. 
    • Applications: Architectural paint testing, testing of industrial coatings, testing of automotive finishes, testing of wood coatings, testing of anti-corrosion primers.

    What are the Uses of the ASTM D1735 Standard?

    The ASTM D1735 test is used to assess the ability of a coating to withstand degradation during continuous water fog exposure. Formulators then use the results to compare coating systems and to predict how a coating will perform over its service life. This standard-

    • Exposes coated specimens to a constant water fog in a controlled environment at a fixed temperature.
    • Uses demineralized water to separate the water resistance from salt corrosion.
    • Evaluates coating damage and permeation due to continuous exposure to moisture.
    • Helps with comparing the water resistance of various coating formulations.
    • Helps to estimate the service life of a coating from its reaction to water fog.
    • Supports coating manufacturing and formulation process.
    • Helps in selecting water fog apparatus configuration for a specific testing program. 

    What Materials Are Covered Under ASTM D1735? 

    ASTM D1735 is used for coated test specimens of various types of coatings, such as architectural paints, industrial coatings, automotive finishes, wood coatings, and anti-corrosion primers. Common applications include formulation comparison tests and service life prediction of coatings for condensation and moisture resistance. Technicians select coated specimens representative of the formulation or product under evaluation.

    Why is ASTM D1735 Important? 

    ASTM D1735 is a standard operating procedure that allows different laboratories to achieve water fog test conditions that are similar to the common apparatus that is available. Coating formulators use this practice because degradation of the coating by exposure to water happens over time, and knowing how well a coating resists water fog gives an idea of the coating’s service life. 

    ASTM D1735 Equipment and Sample Preparation Guide

    ASTM D1735 uses a watertight cabinet, similar to that specified in Practice B117 for salt spray testing, to generate and maintain a controlled water fog environment. Coated specimens are placed in the cabinet for free deposition of fog over the surface of the specimen. The practice defines a chamber temperature of 38°C (100°F) unless otherwise stated, and deposition of the fog at a controlled rate.

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    Sample and Specimen DetailsTechnicians test coated specimens, including architectural, industrial, automotive, or anti-corrosion coatings, prepared for controlled water fog exposure. 
    Specimen PreparationTechnicians coat and cure test panels according to the coating manufacturer’s instructions before placing them in the water fog cabinet. 
    Specimen Positioning and Exposure Conditions Technicians position specimens in the cabinet to allow free fog deposition, with the chamber maintained at 38°C (100°F) and demineralized water falling at 1.5 to 3.0 mL/80cm²/hour. 
    InstrumentationWatertight cabinet compatible with Practice B117 apparatus, demineralized water supply and reservoir, temperature control system, and a fog-generating nozzle assembly. 

    Testing Procedures and Requirements for ASTM D1735  

    Technicians place the coated specimens inside the watertight cabinet and expose them to a continuous, indirect spray of demineralized water falling at 1.5 to 3.0 mL/80 cm²/hour, while the chamber maintains a steady temperature of 38°C (100°F). The test duration, however, depends on the coating system and the requirements of the evaluation program. 

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    Other referenced documents include ASTM D117, D609, D714, D823, D870, D1193, D1654, D1730, D2247, D2616, D3359, D3363, D4541, and D4585.

    Cabinet Preparation Technicians verify the cabinet is clean and, if converted from salt spray use, free of all salt residue before beginning water fog testing. 
    Specimen Placement Technicians position the coated specimens inside the cabinet to allow free, unobstructed fog deposition across each surface. 
    Fog Exposure The cabinet maintains a continuous demineralized water fog at the specified deposition rate and a steady 38°C (100°F) temperature throughout the exposure period. 
    Post-Exposure Evaluation Technicians remove specimens at the specified interval and evaluate them for adhesion loss, blistering, or other coating degradation using related test methods. 
    Result Reporting Laboratories report pass or fail determination and the degree of failure if measured. Results are documented with test conditions and observations.

    ASTM D1735 Process and Data Collection

    Testing starts with technicians applying and curing the test panels following the coating manufacturer’s instructions. Technicians verify the water fog cabinet is clean and free of any salt residue if converted from salt spray use, before positioning the specimens inside to allow free fog deposition. A continuous, indirect spray of demineralized water falls on the specimens at a rate of 1.5 to 3.0 mL/80cm²/hour and the chamber temperature is maintained at a constant 38°C (100°F) throughout the process. Technicians watch the exposure for the duration of the test, the length of which depends on the evaluation program. Lastly, technicians extract the specimens and test them for adhesion loss, blistering, or any other indications of coating deterioration according to the appropriate related test methods. 

    The image depicts coated test panels positioned inside a water fog cabinet undergoing exposure to demineralized water fog as per ASTM D1735.
    ASTM D1735 Water Fog Testing of Coated Specimens

    Common Challenges and Troubleshooting

    Results are often contaminated by incomplete removal of salt residue when technicians change from salt spray to water fog testing, because salt contamination, even at low concentrations, affects the intended demineralized water environment. Inconsistent fog deposition rate or chamber temperature can also affect test severity if technicians don’t monitor and control these conditions closely throughout exposure. If the specimens in the fog chamber are not set in the same positions, then the fog will be in contact with different panels during the same test run. Laboratories solve these problems by cleaning the cabinet and reservoir thoroughly before switching to a new apparatus for use, by checking the temperature and the fog deposition rate regularly, and by carefully placing specimens to ensure even exposure to fog. 

    ASTM D1735 Analysis Results and Interpretation

    This report summarizes the water resistance performance found in the tested coated specimens. It provides exposure time, specimen information, and chamber parameters for testing. This interpretation compares the coating condition and the applicable formulation specification or service life.

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    • The laboratory reports the duration of the exposure and the conditions of the chamber during testing, such as fog deposition rate and temperature.
    • The technician recognizes the type of coating tested and the type of substrate tested, as well as formulation information that is important for assessing water resistance performance.
    • The analyst documents the changes that are observed, including adhesion loss, blistering, etc., using related test methods, e.g., Test Method D3359.
    • The engineer takes into account the porosity of the coating, its surface finish, and length of exposure in interpreting the water resistance results.
    • Formulators use the observed results to support coating service life predictions and formulation comparison decisions. 

    Link to ASTM D1735 

    FAQ

    What does the difference between ASTM D1735, D2247, and D4585 mean?
    ASTM D1735 uses a water fog spray for film wetting, ASTM D2247 uses 100% relative humidity without direct fog spray for pure condensation exposure, and ASTM D4585 uses controlled condensation at elevated temperature, giving formulators three related but distinct water resistance test environments to choose from.
    No, this practice applies to the methods of obtaining, measuring, and controlling the conditions of water fog testing, and the evaluation of the coating condition resulting from the water fog test, such as the determination of adhesion loss by Test Method D3359, uses separate related test methods selected by the evaluation program.
    Yes, the test apparatus is similar to that used in Practice B117 for salt spray testing, and it is possible to convert the apparatus from salt spray to water fog testing, provided that the technicians thoroughly clean the cabinet and reservoir to remove all traces of salt.

    Updated on October 14, 2026

    Davis Scott
    About Author
    Davis Scott
    Davis Scott is an Electrical and Electronics Engineer specializing in multidisciplinary validation, quality assurance, and comprehensive electro-mechanical testing.
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