ISO 11997-1 Paints and Varnishes - Determination of Resistance to Cyclic Corrosion Conditions - Part 1: Wet (Salt Mist)/Dry/Moist

The ISO 11997-1 Paints and varnishes - Determination of resistance to cyclic corrosion conditions - Part 1: Wet (salt mist)/dry/damp standard, published by the International Organization for Standardization (ISO), describes a method for determining the resistance of coatings to one of four defined wet (salt mist)/dry/damp condition cycles using the specified solutions.

Coatings of paints, varnishes, and similar materials are exposed to one of the four wet and dry condition cycles specified in this standard, in a cabinet using the specified salt solutions, in order to simulate processes occurring in aggressive outdoor conditions such as marine environments in the laboratory. Generally, a correlation between such outdoor weather conditions and laboratory tests cannot be expected due to the numerous factors influencing the degradation process. A correlation can only be expected if the effect of key parameters (e.g., the nature of the contaminant, the spectral distribution of the incident radiation in the relevant photochemical region, the temperature of the sample, the type and cycle of wetting, and relative humidity) on the coating is known.

Unlike outdoor weather conditions, laboratory tests conducted inside a booth are performed with fewer controllable variables, and therefore the effects are more repeatable. The described method can also provide a way to check whether the quality of a paint or paint system is being maintained.

The test cycles included in this standard are as follows:

• Cycle A: This cycle is specified in the Japanese automotive standards JASO M 609-91 and JASO M610-92.
• Cycle B: This cycle is based on the VDA 621-415 standard cycle and is widely used in Europe. It has also been shown to provide good correlation against natural weathering for thermoset paints in vehicle corrosion.
• Cycle C: This cycle was developed in the UK for use with water-soluble and latex paint systems and has been shown to correlate well with natural weathering.
• Cycle D: This cycle is specified in the Japanese standard JIS K 5621-2003.

In the protective coatings industry, where paints, varnishes, and coatings must withstand aggressive environments such as automotive, marine, or industrial settings, standardized testing for reliability and longevity is vital. ISO 11997-1 is a fundamental standard addressing the determination of resistance to cyclic corrosion conditions, focusing on alternating wet (salt mist), dry, and wet phases without UV exposure.

This standard helps manufacturers simulate accelerated real-world degradation to predict coating performance. The ISO 11997-1 standard provides a controlled and reproducible protocol highlighting corrosion mechanisms caused by salt, moisture, and temperature fluctuations.

This standard applies to organic coatings on metallic surfaces and evaluates defects such as blistering, rusting, or loss of adhesion. Key characteristics include:

• A neutral salt solution (usually 5 percent sodium chloride) is used to ensure consistency.
• Flexibility in cycle durations to accommodate specific exposure intensities.
• Guidelines for reservoir calibration and panel preparation, along with an emphasis on reproducibility between laboratories.

The procedure involves exposing coated test panels to a special cyclical corrosion chamber that automates the phase transitions. The panels are typically made of steel, aluminum, or user-specified metals, coated according to manufacturer specifications, and usually inscribed to assess leakage beneath the film. This method essentially involves the following steps:

• Sample preparation: Coatings are applied evenly (e.g., by spraying or dipping) to achieve the target dry film thickness (typically 50-100 μm). Reference panels with known performance are added for comparison. To initiate corrosion zones, a cross-line (X-cut or linear scratch) is applied from the coating to the substrate according to ISO 17872 standard.
• Cyclic exposure sequence: The core cycle involves alternating three phases repeated over a specified number of cycles (e.g., 6-24 weeks or until a predefined failure). A standard weekly cycle is as follows:
• Wet (salt mist): Conditions: Spray of atomized salt solution. Duration: 0,5-2 hours daily. Temperature: 35 ± 2 degrees Celsius, relative humidity: 100% (saturated). Purpose: To deposit salt for electrolytic corrosion by simulating exposure to marine or road salt.
• Drying: Conditions: Forced air drying. Duration: 4-8 hours. Temperature: 60 ± 2 degrees Celsius, relative humidity: 30%. Purpose: To promote substrate corrosion and cracking by condensing the electrolytes.
• Humidity: Conditions, condensed moisture. Duration, remaining time (e.g., 16-18 hours). Temperature 50 plus/minus 2 degrees, relative humidity 95-100 percent. Purpose: To trigger moisture absorption, causing swelling or delamination.

Variations, such as more than one wet-dry pass per day, allow sub-cycles to increase the testing speed. The chambers need to provide precise controls where the salt solution pH is between 6,5 and 7,2.

• Evaluation and reporting: After placement, the panels are cleaned and visually and mechanically evaluated. The basic criteria are as follows:
• Line yield: Measured according to ISO 4628-8 standard (e.g., at least 2 mm usually indicates a passing grade).
• Bubbling: Graded according to size and density (scale 0-5 according to ISO 4628-2 standard).
• Degree of corrosion: Percentage of corroded surface (according to ISO 4628-3 standard).
• Adhesion: Tensile or tape tests are performed after exposure.

Photographic documentation and statistical analysis ensure objective reporting.

The ISO 11997-1 standard is essential for industries requiring robust corrosion protection:

• Automotive: Determining the adequacy of chassis or body coatings against winter road salts and humidity in varying climates.
• Infrastructure: Testing bridge paints or pipeline coatings against cyclical wet-dry exposure in temperate regions.
• Consumer goods: Evaluating the durability of appliance coatings in humid environments.
• Aerospace and defense: Evaluation of military vehicle coatings where UV corrosion is secondary.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the “ISO 11997-1 Paints and varnishes - Determination of resistance to cyclic corrosion conditions - Part 1: Wet (salt spray)/dry/moist” standard.