The core reasons for chalking/fading of color-coated steel sheets:
1. Raw material defects
Substrate problems: Rust or incomplete cleaning of the steel sheet surface (residual oil/impurities) leads to poor coating adhesion, making it prone to chalking and peeling.
Poor coating materials: Resin is not weather-resistant: Low-end polyester resin (PE) has weak UV resistance and is easily decomposed and chalked; Inferior pigments: Inorganic pigments have poor lightfastness (such as some red and yellow pigments), making them prone to fading.

2. Substandard Production Process
Insufficient Pretreatment: Incomplete degreasing, phosphating, or passivation results in weak adhesion between the substrate and coating; Uneven Coating Thickness: Too thin (≤15um) easily powders, too thick (>30um) easily cracks; Incomplete Curing: Insufficient baking temperature or time prevents sufficient resin cross-linking, reducing weather resistance.

3. Environmental Corrosion: UV Radiation: Long-term exposure leads to resin decomposition (powdering) and pigment oxidation (fading). Acid/Alkali/Salt Spray Corrosion: Industrial exhaust gases and coastal salt spray corrode the coating surface. Large Temperature and Humidity Differences: Repeated thermal expansion and contraction cause coating cracking, allowing moisture to penetrate and corrode the substrate.

Regular inspection of color-coated steel sheets is necessary to promptly detect and address issues such as coating peeling and corrosion, extending their service life. Regular cleaning of the color-coated steel sheet surface is also crucial to remove dust, dirt, and other contaminants, maintaining its appearance and weather resistance. At the same time, avoid using strong corrosive cleaning agents to prevent damage to the coating.

The powdering rate not only affects the aesthetics of color-coated steel sheets but also directly impacts their service life and performance.

The powdering rate of color-coated steel sheets refers to the degree to which the coating on the surface of color-coated steel sheets powders under certain conditions. Chalking refers to the phenomenon where fine powder appears on the surface of a coating, causing the coating to lose its gloss, change color, or even peel off. A higher powdering rate indicates a lower coating quality and a shorter service life.

Factors affecting the chalking rate of color-coated steel sheets:
1. Coating quality: The quality of the coating is a key factor affecting the chalking rate. High-quality coatings have better weather resistance, corrosion resistance and adhesion, and can effectively reduce chalking rate.
2. Construction process: The construction process of color-coated steel sheets will also affect the powdering rate. A proper construction process can ensure a uniform and dense coating, thereby improving the coating's durability.
3. Usage environment: The usage environment of color-coated steel sheets is also an important factor affecting the powdering rate. Harsh environments such as high temperature, high humidity, and strong ultraviolet radiation can accelerate the chalking process of the coating.

Generally speaking, the chalking rate of high-quality color-coated steel sheets should be below a certain value, and the specific value varies depending on different products and application scenarios. When purchasing color-coated steel sheets, attention should be paid to the product's chalking rate index, and products that meet industry standards should be selected.

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