1.What are the testing standards and principles of a salt spray test chamber?
Test Standards: ASTM B117, ISO 9227, JIS Z 2371, etc.
Test Principle: In a sealed chamber, a 5% sodium chloride solution is atomized by compressed air to form a uniform salt spray that settles on the sample surface, while maintaining a constant temperature (typically 35°C).
Simulated Environment: Marine atmosphere or road environment with de-icing agents applied in winter.
Evaluable Items:
White Rust Formation Time: This is a key indicator of the corrosion resistance of the galvanized layer. The longer the time, the better the corrosion resistance. Standards typically require no white rust after >48 hours or 72 hours.
Red Rust Formation Time: The time from the start of the test to the appearance of red rust on the base steel. The longer this time, the longer the overall protective life of the galvanized layer.
2.What are the testing standards and principles of the cyclic corrosion test chamber?
Testing Standards: ASTM D6899, ISO 11997, SAE J2334, etc.
Test Principle: It's not just about spraying salt spray; it simulates the natural cycle of wet and dry conditions. A typical cycle might include: salt spray → drying → wet.
Advantages: Because it includes a drying period, the test results correlate much better with actual outdoor exposure than traditional continuous salt spray tests, making it considered a more scientific testing method.
3.What are the testing standards and principles for damp heat test chambers?
Test Standard: ISO 6270-2 (CH conditions), etc.
Test Principle: The corrosion resistance of the galvanized coating is tested under high temperature and high humidity conditions (e.g., 40℃, 93% RH). This primarily assesses the tendency to develop "white rust" in humid, poorly ventilated environments.
Application: Ideal for testing the surface white rust problem of galvanized coils caused by condensation during storage and transportation.
4.What are the testing methods for outdoor atmospheric exposure test stations?
Test Method: Zinc-plated coil samples are cut into standard-sized test pieces and placed in outdoor test environments, such as:
Rural Atmosphere: Low pollution, slower corrosion.
Urban/Industrial Atmosphere: Contains acidic gases such as SO2, faster corrosion.
Marine Atmosphere: Contains chloride ions, rapid corrosion.
Evaluation: Samples are taken periodically (e.g., every 1, 2, 5, and 10 years) to observe surface corrosion, measure zinc layer thickness loss, and record the time when red rust appears.
Characteristics: Results are the most realistic and reliable, serving as a benchmark for validating accelerated testing methods; however, meaningful data may take years or even decades to obtain.
5.What are the testing process and evaluation methods?
Sample Preparation: Cut representative test pieces from the galvanized coil.
Initial Measurement: Measure the original galvanized layer thickness of the sample (using a magnetic or eddy current thickness gauge), which is the most important parameter for predicting its lifespan.
Testing: Place the sample in the aforementioned equipment and conduct tests according to standards.
Result Evaluation:
Visual Inspection: Regularly observe the surface for white rust, red rust, and their covering area.
Adhesion Test: After testing, use the tape method to check for peeling or flaking of the zinc layer.
Zinc Corrosion Weight Loss: After testing, dissolve the corrosion products chemically and accurately calculate the weight loss of the zinc layer per unit area.