ISO 9227
ISO 9227 Salt Spray Corrosion Testing
ISO 9227 salt spray testing, also referred to as ISO 9227 salt mist testing, is used to evaluate the corrosion resistance of metallic materials and protective coatings under controlled laboratory conditions. Based in Montreal, Micom Laboratories provides ISO 9227 testing as part of its corrosion testing services, including Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), and Copper-Accelerated Acetic Acid Salt Spray (CASS). These test methods help manufacturers evaluate coating performance, identify corrosion defects, and compare test results against applicable product or customer requirements.
What is ISO 9227 Salt Spray Testing?
ISO 9227 is an international standard that defines methods for conducting salt spray (salt fog) tests in artificial atmospheres. You may also see the standard referenced as DIN EN ISO 9227, particularly in European or German specifications.
This form of accelerated corrosion tests exposes samples to a fine mist of salt solution under controlled temperature and humidity conditions to simulate corrosive environments.
ISO 9227 corrosion testing is particularly useful for detecting discontinuities, pores and defects in organic and inorganic coatings as well as for assessing the corrosion resistance of metallic materials. It is also widely used to compare the performance of coated and uncoated materials under standardized test conditions.
ISO 9227 Salt Spray Test Methods: NSS, AASS and CASS
There are three distinct test methods in ISO 9227:
- The Neutral Salt Spray test (NSS)
- The Acetic Acid Salt Spray test (AASS)
- The Copper-Accelerated Acetic Acid Salt Spray test (CASS)
Typically, the NSS test applies to metals and their alloys, metallic coatings (anodic and cathodic), conversion coatings, anodic oxide coatings and organic coatings on metallic materials. As for the AASS and CASS tests, they are especially useful for testing decorative coatings made of copper, nickel and chromium or only nickel and chromium. AASS and CASS have also been found to be suitable for testing anodic coatings on aluminum.
Test Conditions and Parameters for ISO 9227 Testing
The test conditions for an ISO 9227 salt spray test depend on whether the required method is NSS, AASS, or CASS. Test duration, specimen quantity, acceptance criteria, and evaluation method are typically defined by the applicable product standard, customer specification, or qualification requirement.
Experimental parameters for ISO 9227 testing
| Test Method Item | Neutral Salt Spray (NSS) | Acetic Acid Salt Spray (AASS) | Copper-Accelerated Acetic Acid Salt Spray (CASS) |
| Temperature | 35 oC ± 2 oC | 35 oC ± 2 oC | 50 oC ± 2 oC |
| Average collection rate for a horizontal collecting area of 80 cm2 | 1,5 mL/h ± 0,5 mL/h | ||
| Concentration of sodium chloride (collected sodium) | 50 g/L ± 5 g/L | ||
| pH (collected solution) | 6.5 to 7.2 | 3.1 to 3.3 | 3.1 to 3.3 |
| Number of test specimens | To be specified, typically 1 | ||
| Shape and size of specimens | To be specified, typically 75 x 150 mm | ||
| Arrangement of the test specimens | The specimen must be flat and placed in the cabinet, facing upwards, at an angle as close as possible to 20° to the vertical. This angle shall, in all cases, be within the limits 15° to 25°. | ||
| Duration of tests | To be specified. Typical exposure periods are 2 h, 6 h, 24 h, 48 h, 96 h, 168 h, 240 h, 480 h, 720 h, 1 000 h, and 2000 h. | ||
Materials and Coatings Commonly Tested to ISO 9227
ISO 9227 testing is commonly applied to metallic materials, plated components and coated products where corrosion resistance, coating integrity, and surface performance need to be evaluated under standardized test conditions.
Examples of materials and coatings tested:
- Electroplated components (zinc, nickel, chromium)
- Anodized aluminum
- Painted and powder-coated metal parts
- Conversion coatings and passivated surfaces
- Decorative and functional coatings
These materials are frequently used in environments where corrosion resistance is essential for performance, safety, and appearance.
Industry Applications of ISO 9227 Testing
ISO 9227 Salt spray corrosion testing is widely used across multiple industries. Micom Laboratories is happy to support the following industries with their corrosion testing needs.
- Automotive: fasteners, trim, underbody components
- Electronics: enclosures, connectors, housings
- Industrial equipment: coated assemblies and machinery parts
- Consumer products: appliances, hardware, decorative finishes
- Marine and offshore: corrosion-prone components
When to Use ISO 9227 Testing
ISO 9227 testing is most appropriate when manufacturers need a controlled, repeatable method to compare corrosion resistance between materials, coatings, suppliers, or production batches.
- Comparative evaluation of coating systems
- Quality control during production
- Supplier and material validation
- Identifying coating defects and weaknesses
It is particularly useful when consistent, repeatable laboratory conditions are required to compare performance across samples.
Limitations of Salt Spray Testing
While ISO 9227 is widely used, it is important to understand its limitations. There is no direct correlation between resistance to salt-spray and resistance to real-word corrosion, as the corrosion stresses in end-use conditions differ significantly from those during testing. In this way, results should not be used as a direct predictor of long-term real-world behavior or as the sole basis for ranking different coating systems.
ISO 9227 vs ASTM B117 vs ASTM G85
| Standard | ISO 9227 | ASTM B117 | ASTM G85 |
| Key Use | International salt spray standard | Widely used baseline salt spray test – American Standard | Modified / cyclic corrosion testing |
| Environment | NSS, AASS, CASS methods | Continuous salt fog | More realistic environments |
Correspondence between standards:
- The Neutral salt spray test (NSS) specified in ISO 9227 is equivalent to ASTM B117, with the same test conditions being used. However, the specimen positions during testing must be between 15° and 25° for ISO 9227 and between 15° and 30° for ASTM B117.
- The Acetic acid salt spray (AASS) in ISO 9227 is equivalent to the Acetic acid-salt spray test in annex A1 of ASTM G85. Nevertheless, the position of specimens during exposure must be between 6 and 45° for ASTM G85, while it must be between 15° and 25° for ISO 9227.
- The Copper-Accelerated Acetic Acid Salt Spray (CASS) is equivalent to ASTM B368, with the same test conditions. However, the specimens must be positioned between 15° and 30° from the vertical in ASTM B368, while it is between 15° and 25° for ISO 9227.
- While specimen position varies with the test, studies in our corrosion testing lab on standardized reference specimens showed that sample orientation has no significant impact on the corrosion rate. Choosing the right test depends on your product, coating system, and required performance criteria.
ISO 9227 Evaluation of Results
After exposure, various criteria may be applied to meet particular requirements:
- Appearance after the test
- Appearance after removing superficial corrosion products
- Number and distribution of corrosion defects
- Pits, cracks, blisters, rusting or creep from scratches in the case of organic coatings, etc.
- Assessed by methods described in ISO 8993, ISO 10289 or ISO 4628 (largely equivalent to ASTM D714 and ASTM D610)
- The time elapsing before the appearance of the first signs of corrosion
- Change in mass
- Alteration revealed by micrographic examination
- Change in mechanical properties
Why Choose Micom Laboratories for ISO 9227 Testing
Micom Laboratories provides ISO 9227 testing services to organizations that need to evaluate the corrosion resistance of metallic materials, protective coatings, plated components, and finished products under controlled laboratory conditions.
We offer:
- NSS, AASS, and CASS testing capabilities
- Detailed reporting and performance evaluation
- Support for product qualification and failure analysis
- Fast turnaround and responsive technical support
Our team works closely with manufacturers, engineers, and quality professionals to deliver reliable, repeatable, and actionable test results.
Request a Quote for ISO 9227 Testing
Whether you are validating a new coating system, comparing materials, qualifying a supplier, or meeting a customer specification, our material testing lab can help you determine the appropriate ISO 9227 salt spray testing approach.
We can review your requirements, confirm whether NSS, AASS, or CASS testing is suitable for your project, and provide clear reporting to support your technical or compliance needs.
Send us your specifications or project details, and our team will help you define the next step.
Frequently Asked Questions
What is the ISO 9227 neutral salt spray test?
The ISO 9227 neutral salt spray test, or NSS test, is a salt spray corrosion test performed using a neutral sodium chloride (NaCl) solution. It is commonly used to evaluate metallic materials, plated components, conversion coatings, painted surfaces, powder-coated parts, and other protective coating systems.
What is ISO 9227 used for?
ISO 9227 is used to evaluate the corrosion resistance of metallic materials and coatings using salt spray exposure under controlled laboratory conditions.
What are the differences between NSS, AASS, and CASS?
NSS uses a neutral salt solution, AASS introduces acetic acid for increased aggressiveness, and CASS adds copper chloride to further accelerate corrosion.
How long does ISO 9227 testing take?
Test duration can range from 24 hours to over 1000 hours, depending on product requirements and specifications.
Does ISO 9227 predict real-world corrosion?
Not exactly. It is best used for comparative testing rather than predicting actual service life in real environments.
What materials can be tested?
Common materials include plated metals, anodized aluminum, painted surfaces, and coated components.
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