ASTM D870 Standard Practice for Testing Water Resistance of Coatings Using Water Immersion

ASTM D870 Introduction

ASTM D870 (Standard for Testing Water Resistance of Coatings Using Water Immersion) is a widely accepted method, as water immersion can damage coatings and affect their service life. It predicts failures due to coating deficiencies, substrate contamination, or inadequate surface preparation. Water immersion tests aid in coatings and substrate treatment research, specification acceptance, and manufacturing quality control. It is used for research and quality control, and it determines pass/fail based on damage resistance over time. Accelerating corrosion processes like pitting, it helps engineers predict coating effectiveness before service.

Other test methods to evaluate water resistance include ASTM D1735 (water fog), ASTM D2247 (100% humidity), and ASTM D4585 (controlled condensation

Get Certified ASTM D870 for Uncompromising Quality and Project Success

ASTM D870 certification proves a laboratory can accurately measure coating water resistance through controlled immersion. It guarantees compliance with global standards, ensuring consistent results across manufacturers. By using this certified method, companies assess durability, identify weaknesses, and verify specifications. This certification boosts product reliability, market acceptance, and quality assurance.

The images shows the equipment for water immersion testing by astm d870. — Water Immersion Testing Equipment

What is the Scope of ASTM D870?

Guides testing protocols to evaluate how well coatings withstand continuous water immersion.
Ensures reliable and uniform assessment of water-induced coating degradation.
Suited for both experimental research and industrial quality assurance applications.
Compatible with both manual and computerized environmental testing equipment.

What is the equipment requirement and Sample Preparation for ASTM D870

Specimen Details	A control specimen of paint with known durability is used in each test. Such control specimens reflect variations in test severity between several apparatuses and can signal changes in test severity in a specific apparatus. To account for variations among specimens and test conditions within the apparatus, at least two replicated specimens of each coating type are used.
Substrate Material	Metal (steel, aluminum), wood, or plastic panels, depending on coating type. Substrate must be compatible with the coating system.
Specimen Dimensions	Common dimensions range from 75 × 150 mm to 100 × 150 mm, or as specified by the coating manufacturer. Panels must fit without touching tank walls or other specimens.

What are the uses of ASTM D870

• Testing of marine, industrial, and architectural protective coating.

• Confirmation of the performance of corrosion protection.

• Clear coat, primer, and topcoat testing in the automotive and aerospace market.

• Studies of waterborne finishes and new protection compositions.

• Coating performance measurement under the humid, wet, or submerged conditions.

What are the Common Challenges and Troubleshooting

Uneven curing, temperature fluctuations, contaminated water, and incorrect exposure times often cause problems. Mishandling specimens after immersion can also distort results. To reduce variability, laboratories control the pre-test environment and prevent air bubbles. Using automated immersion tanks with temperature control, adhering to strict curing protocols, and replacing water regularly increases testing reliability. Calibrated heaters and gauges maintain a consistent 35 °C in the salt spray chamber to ensure steady corrosion rates and reliable rust development. Standardized evaluation criteria and trained inspectors ensure consistent assessments of coating performance.

Testing Technique, Process, and Data Collection

Data collection involves documenting the frequency and intensity of defects using standardized rating scales. Photographic documentation and measurements of mass or dimensional shifts are recorded for comparison in evaluation. This data is essential for categorizing the performance of coatings and establishing a link between test results and anticipated environmental durability.

What are the Testing Procedures and Requirements?

In the ASTM D870 testing procedure, coated specimens are immersed in water (distilled or saline) under controlled temperature conditions for a specified duration. Defects such as blistering, peeling, or corrosion are periodically inspected to assess coating performance.

Preparation of Coated Panels	Apply coating uniformly on clean substrates; allow full curing; ensure consistent film thickness and defect-free surfaces.
Water Immersion Setup	Immerse panels fully in distilled/deionised water; maintain controlled temperature (25–38°C); ensure no trapped air bubbles.
Exposure Duration	Keep specimens submerged for the specified time (24 hours to several weeks), depending on coating performance requirements.

Analysis Results and Interpretation

ASTM D870 test shows how coatings respond to prolonged exposure to water immersion, identifying specific failures such as film softening, loss of adhesion, and osmotic blistering. Adequate interpretation depends on proper assessment of the severity of defects against established rating standards. These results serve as a critical justification for determining whether a coating is suitable for use in wet or submerged environments.

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Updated on May 1, 2026

About Author

Gokula Srinivasan Selvam

Gokula Srinivasan Selvam is a Material Testing Associate at Matestlab Inc. and holds a postgraduate degree in Ceramic Engineering from IIT (BHU), Varanasi. His academic background and professional experience are centered on advanced ceramic materials, their processing, characterization, and performance evaluation.
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ASTM D870 Standard Practice for Testing Water Resistance of Coatings Using Water Immersion

ASTM D870 Introduction

Get Certified ASTM D870 for Uncompromising Quality and Project Success

What is the Scope of ASTM D870?

What is the equipment requirement and Sample Preparation for ASTM D870

What are the uses of ASTM D870

What are the Common Challenges and Troubleshooting

Testing Technique, Process, and Data Collection

What are the Testing Procedures and Requirements?

Analysis Results and Interpretation

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