The evaluation of salt spray test results typically involves visually inspecting the test specimens after exposure to the salt-laden environment. The appearance and extent of corrosion are assessed based on standardized criteria. Here's an example of how the results of the salt spray test can be evaluated:
1. Rating System: The evaluation often employs a rating system, such as the ASTM D610 or ISO 4628 standards, to assign a corrosion rating based on the observed corrosion effects. These standards provide a set of standardized grades or levels to quantify the extent of corrosion damage.
1. Corrosion Features: The test specimens are examined for various corrosion features, which may include:
a. Rust Formation: The presence of visible rust or iron oxide on the surface of the specimen.
b. Blistering: Formation of blisters or bubbles in the coating, indicating corrosion beneath the surface.
c. White Rust: A powdery white corrosion product commonly observed on zinc or zinc-coated surfaces.
d. Red Rust Staining: Discoloration or staining caused by rust that may be present on adjacent areas.
1. Rating Scale: The rating scale assigns a numerical or descriptive grade to each specimen based on the observed corrosion effects. The scale may range from 0 (no corrosion) to higher numbers or grades indicating increasing levels of corrosion damage.
1. Reporting: The results of the evaluation are typically documented in a test report, which includes details such as the test duration, test conditions, specimen identification, and the assigned corrosion rating for each specimen.
For example, a test report might indicate that a coated metal specimen achieved a corrosion rating of "Grade 8" after 500 hours of salt spray exposure. This rating would suggest a relatively high level of corrosion damage compared to a lower-grade rating.
It's important to note that the specific evaluation criteria and rating scales may vary depending on the applicable standard or industry requirements. Therefore, it is essential to refer to the relevant standard or specification that governs the salt spray test for accurate evaluation and comparison of results.