Cathodic dip coating (E-coat) forms the foundation of corrosion protection in the automotive industry. It ensures the long-term durability of vehicle bodies and individual components, which is why its quality is continuously verified through corrosion testing. One of the most commonly used methods is the salt spray test, which quickly reveals weak points in the coating. At Automotive Painting Partners, we perform this test in-house, giving customers confidence that their parts can withstand even demanding operating conditions.
The ČSN EN ISO 9227 standard and its three variants
The salt spray test is standardised according to ČSN EN ISO 9227, which defines three basic types of tests differing in environmental aggressiveness:
- NSS (Neutral Salt Spray) – the most widely used test with a neutral NaCl solution (5%, pH 6.5–7.2). Suitable for evaluating intact coatings and detecting defects such as pores or uneven thickness.
- AASS (Acetic Acid Salt Spray) – the NaCl solution is acidified with acetic acid (pH 3.1–3.3). This more aggressive environment enables faster evaluation of coatings sensitive to acidic conditions and is often used for thin organic layers.
- CASS (Copper-Accelerated Acetic Acid Salt Spray) – the most demanding variant, enhanced with copper(II) sulphate. It is used mainly for decorative nickel–chrome coatings.
Testing at APP: two corrosion chambers and one condensation chamber
At Automotive Painting Partners, we operate two corrosion chambers and one condensation chamber. This allows us to perform NSS and condensation tests independently on site. AASS and CASS tests are carried out in cooperation with trusted external laboratories. Thanks to this combination, we can guarantee our customers that their parts achieve consistently excellent corrosion resistance.
Benefits of salt spray testing
The main advantages of these tests:
- rapid identification of defects and weak points in the E-coat layer,
- detection of issues in surface pretreatment or coating application,
- standardised and repeatable conditions – enabling comparison of results across manufacturers and suppliers,
- applicability in both early development stages and serial production for routine quality control.
For engineers and technicians, the tests represent a reliable tool for verifying coating quality before components enter service.
Limitations and proper interpretation of results
The salt spray test also has limitations. In the chamber, the sample is exposed to continuous salt aerosol at a constant temperature. This scenario differs significantly from real-world conditions, where humidity and dryness alternate, temperatures fluctuate, and mechanical impacts (e.g. stone chipping) also occur.
Therefore, results cannot be directly translated into the real-life service life of a coating. For more comprehensive evaluation, cyclic corrosion tests are also used, as they simulate real conditions more accurately. Although these are more time and cost-intensive (400–900 hours), they provide a much clearer picture. At APP, we provide these in cooperation with external laboratories, allowing us to offer customers comprehensive testing services.
Why salt spray alone is not enough
The salt spray test according to ČSN EN ISO 9227 is a proven and fast way to detect defects in E-coat layers. However, it is only one tool in the broader assessment process – true reliability comes from a comprehensive approach that incorporates multiple types of testing.
The right combination of methods gives engineers and technicians confidence when assessing the durability of protective systems, not only in the automotive industry but also across other sectors – from mechanical engineering and agricultural or construction machinery to medical technology.
Do you want assurance that your parts will perform even under the most demanding conditions? Contact us – we will provide comprehensive testing and guarantee top-level corrosion resistance.
