1.What are the core assessment methods?
Depending on the type of pollution, pollution resistance assessment can be divided into three categories: daily stain test, chemical pollutant test and natural exposure test, among which laboratory simulation test is the most commonly used method.
2.What are the experimental steps for daily stain adhesion and removal testing?
Select standard stains (such as carbon black suspension to simulate dust, engine oil to simulate grease, red ink to simulate colored liquid, ketchup/soy sauce to simulate food stains, etc.);
Evenly apply the stains on the surface of the color-coated coil sample (usually an area of 50mm×50mm), and leave it in a standard temperature and humidity environment (23℃±2℃, 50%±5% RH) for a certain period of time (such as 24 hours, 72 hours, to simulate stain penetration);
Remove the stains according to the prescribed method (such as rinsing with clean water, wiping with a soft cloth, or adding a small amount of neutral detergent), and avoid excessive force to damage the coating;
Compare the sample surface before and after cleaning to evaluate the degree of residual contamination.
3.What are the experimental steps for chemical contaminant testing?
Select representative chemical reagents (such as 5% sulfuric acid solution to simulate acid rain, 10% sodium hydroxide solution to simulate alkaline pollution, 3% sodium chloride solution to simulate salt spray environment, etc.);
Drop the reagent on the surface of the sample (or cover the sample with filter paper soaked with the reagent), cover it with a glass dish to prevent volatilization, and let it stand for a specified time (such as 24 hours, 96 hours);
Remove the reagent and wipe it dry, and observe whether the coating changes color, bubbles, softens, peels off, or exposes the bottom.
4.What are the natural exposure test procedures?
Expose the specimen at a certain angle (e.g. 45°, facing due south) in an outdoor test field (such as the exposure conditions specified in GB/T 9276), and observe the surface contamination adhesion periodically (e.g. 3 months, 6 months, 1 year); Clean the specimen regularly (according to routine maintenance methods), and record the cleaning difficulty and appearance changes.
5.What are the key factors affecting pollution resistance?
Coating type: Fluorocarbon coating (PVDF) has lower surface tension, stronger chemical stability, and better stain resistance than polyester (PE) or epoxy coating;
Surface treatment: High surface smoothness (such as mirror effect) or the addition of anti-fouling additives (such as nano coating) can reduce stain adhesion and improve easy cleaning;
Coating thickness: Thicker coating (such as ≥25μm) can reduce the risk of stain penetration, but too thick may lead to reduced flexibility.