Salt Spray Testing
During salt spray testing, a sample is placed in a chamber that simulates a highly corrosive environment, and then exposed to a saltwater mist for a set period of time. The conditions within the chamber are controlled, and the test is conducted at a specified temperature and humidity level.
After exposure to the saltwater mist, the sample is examined for signs of corrosion or coating degradation. The test results are typically measured by the appearance of corrosion, either by visual inspection or by measuring the weight loss of the sample.
Salt spray testing is a common industry standard test, and the results are used to assess the durability and performance of coatings and finishes used in a variety of products such as automobiles, electronic components, and outdoor equipment.
Basic Procedure
During the salt spray testing process, test pieces made of ferrous and non-ferrous materials, as well as coated exposure panels, are placed in a closed chamber. The chamber exposes the specimens to a continuous, indirect spray of a salt solution. This solution is made by dissolving approximately 5 parts by mass of sodium chloride in 95 parts by mass of de-ionised water. The temperature inside the exposure zone of the chamber is maintained at 35.0°C ± 2°C.
The duration of the salt spray test depends on the specific application standard or the customer's requirements. The corrosion on each specimen is evaluated every 24 hours, and the details are recorded. At the end of the specified test period, a final evaluation is made in accordance with the applicable standard or customer specification. A detailed test report is then provided, which includes pictures. The purpose of this report is to analyze the quality of the coating or finish, as well as to determine the level of corrosion resistance or susceptibility that the product may experience over time in real-life conditions.
Test Methods
ASTM B117 and EN ISO 9227 are international standards that provide guidance for salt spray testing. ASTM B117 is a standard practice for operating salt spray (fog) apparatus, while EN ISO 9227 specifies a method for salt spray corrosion tests in artificial atmospheres. Both standards provide detailed instructions on the preparation of test specimens, test conditions, and the evaluation of results. These standards help ensure that salt spray tests are conducted consistently and accurately across different laboratories and industries.