How to Detect the Quality of PVDF Coated Aluminum Coil？

How to Detect the Quality of PVDF Coated Aluminum Coil

In the construction, industrial, and decorative sectors, PVDF color coated aluminum coil are widely used in roof structures, curtain walls, billboards, and containers due to their excellent corrosion resistance, weather resistance, and aesthetics. However, due to the special nature of the coating material, quality control of PVDF color coated aluminum coil is particularly important. This article will how to detect the quality of PVDF color coated aluminum coil, covering aspects such as visual inspection, physical performance testing, chemical performance testing, and industry standards, to help users understand how to ensure product quality.

1. Visual Inspection

Visual inspection is the first step in assessing the quality of PVDF color coated aluminum coil, and it is the most direct way to make an initial judgment. By observing with the naked eye, we can preliminarily determine whether the coating is uniform and flat, and whether there are any defects.

1.1 Coating Uniformity

l Coating Thickness: The coating thickness should be uniform, with no obvious thick or thin areas. According to the national standard GB/T17748, the dry film thickness of PVDF coating should be ≥25μm (two coats) or ≥32μm (three coats).

l Surface Flatness: The coating surface should be flat, with no wavy, bulging, or concave defects. Wavy and bulging are not allowed, while minor defects (≤3mm) should not exceed 3 per square meter.

1.2 Color Difference

l Color Consistency: The coating color should be uniform and vibrant, with no obvious color difference. The color difference value (ΔE) should be ≤2.0 to ensure consistency with the design requirements.

l Gloss Level: The gloss level should be consistent, with a deviation of ≤10. Higher gloss indicates better coating quality.

1.3 Surface Defects

l Scratches and Scratches: Scratches and scratches are not allowed, as these defects can affect the adhesion and durability of the coating.

l Bubbles and Pinholes: The coating surface should not have bubbles or pinholes, as these can affect the sealing and corrosion resistance of the coating.

l Stain Lines: The coating surface should not have stain lines, as these can lead to a lower coating thickness, affecting the service life.

2. Physical Performance Testing

Physical performance testing is an important means of assessing the quality of PVDF color coated aluminum coil, including film thickness, adhesion, flexibility, pencil hardness, and abrasion resistance.

2.1 Film Thickness Testing

l Film Thickness Measurement: Use a film thickness gauge to measure the coating thickness, ensuring it meets the standard requirements. For example, the dry film thickness of PVDF coating should be ≥25μm (two coats) or ≥32μm (three coats).

l X-ray Testing: For thicker coatings, an X-ray testing instrument can be used for non-destructive testing to ensure the coating thickness is uniform.

2.2 Adhesion Testing

l Grid Test: Cut the sample into 5mm×5mm squares, and observe whether the coating is intact without peeling or cracking.

l Tape Test: Apply tape to the coating surface and quickly remove it; if there is residual coating on the tape, it indicates poor adhesion.

l Blade Test: Use a blade to scrape the coating surface; if there is peeling, it indicates poor adhesion.

2.3 Flexibility Testing

l Flexibility: The coating should have good flexibility, typically requiring ≤2T (T is the thickness of the sample).

l Bending Test: Bend the sample to a certain angle and observe whether the coating cracks or peels off.

2.4 Pencil Hardness Test

l Pencil Hardness: The pencil hardness of the coating should be ≥HB to ensure good scratch resistance.

l Hardness Tester: Use a hardness tester to measure the coating's hardness, ensuring it meets the standard requirements.

2.5 Abrasion Resistance Testing

l Abrasion Resistance: The coating should have good abrasion resistance, typically requiring ≥5L/μm.

l Friction Test: Use a friction tester to measure the coating's abrasion resistance, ensuring it remains intact during use.

3. Chemical Performance Testing

Chemical performance testing is an important means of assessing the corrosion resistance and weather resistance of PVDF color coated aluminum coil, including acid resistance, salt spray resistance, solvent resistance, etc.

3.1 Acid and Alkali Resistance Testing

l Acid Test: Place the sample in 5% HCl solution and observe for any abnormal phenomena such as bubbling, bulging, or powdering.

l Alkali Test: Place the sample in 5% NaOH solution and observe for any abnormal phenomena such as bubbling, protrusion, or powdering, while the color difference should be ≤2.0.

3.2 Salt Spray Resistance Testing

l Salt Spray Test: Place the sample in a salt spray test chamber and observe the coating's resistance to salt spray corrosion. Typically, the requirement is 4000 hours without change.

l Salt Spray Tester: Use a salt spray tester to conduct the test, ensuring the coating maintains good performance in high-salt environments.

3.3 Solvent Resistance Testing

l Solvent Resistance: The coating should have good solvent resistance, typically requiring 200 cycles without delamination.

l Solvent Test: Immerse the sample in a solvent and observe for any peeling or cracking of the coating.

3.4 Nitric Acid Resistance Testing

l Nitric Acid Test: Place the sample in 70% nitric acid and observe for any abnormal phenomena such as bubbling, bulging, or powdering.

l Nitric Acid Tester: Use a nitric acid tester to conduct the test, ensuring the coating maintains good performance in strong acidic environments.

4. Industry Standards and Testing Methods

To ensure the quality of PVDF color coated aluminum coil, it is necessary to follow relevant industry standards and testing methods.

4.1 National Standards

l GB/T17748: This is the Chinese national standard, specifying the technical performance parameters of colored aluminum sheets, including color difference, gloss level, coating thickness, and adhesion.

l AAMA 621-02: Applies to the use of high-performance organic coatings on rolled aluminum coatings for architectural applications of hot-dipped galvanized (HDG) and zinc-aluminum alloy steel.

l ASTM B209: Specifies the chemical composition and mechanical properties of aluminum sheets.

4.2 Third-party Testing

l SGS Testing: SGS is a leading global inspection, certification, and testing institution that can provide third-party testing services to ensure product quality meets international standards.

l Zhongxi Research Institute: The Beijing Zhongke Guangxi Science and Technology Research Institute (Zhongxi Research Institute) provides various material testing methods, including the comprehensive testing of PVDF color coated aluminum coil.

4.3 Testing Process

1.Pre-production Sample Testing: Provide pre-production samples to ensure the product quality meets the requirements.

2.Final Inspection Before Delivery: Conduct a final inspection before shipment to ensure each batch of products meets the standards.

3.Type Testing: Conduct type tests on each batch of products to ensure long-term performance and stability.

5. Conclusion

Detecting the quality of PVDF color coated aluminum coil is a systematic process that involves multiple aspects, including visual inspection, physical performance testing, chemical performance testing, and industry standards and testing methods. By using scientific testing methods and strict quality control, it is possible to ensure that PVDF color coated aluminum coil maintain good corrosion resistance, weather resistance, and aesthetics in practical applications, meeting the needs of different industries and application scenarios.

In practical applications, it is recommended that users choose qualified testing institutions for testing and select appropriate testing items based on their needs. At the same time, manufacturers should establish a complete quality management system to ensure that each batch of products meets national standards and industry requirements, providing high-quality products and services to customers.

References:

1.Technical performance parameters of PVDF color coated aluminum coil

2.Visual inspection and surface treatment methods for PVDF-coated aluminum sheet

3.How to determine the quality of coating aluminum sheets?

4.Enterprise standards for PVDF/Aluminum foil/Back-coated or PE composite film

5.SGS third-party sampling inspection, all performance indicators of Amena PVDF color coated aluminum coil are qualified

6.ASTM B209 Aluminum Coil 2024 3003 Mill Finish 1220mm Width Silver PE PVDF Coated

7.Testing of rolled samples by Zhongxi Research Institute