Why has the phenomenon of color-coated panels fading and rusting become frequent in recent years?
The competition in the color coating industry has reached a boiling point. In Shandong Province's Boxing County alone, there are over 250 coating and plating production lines, leading to severe product homogenization and driving the entire industry into an era of minimal profit margins.
The competition in the color coating industry has reached a boiling point. In Shandong Province's Boxing County alone, there are over 250 coating and plating production lines, leading to severe product homogenization and driving the entire industry into an era of minimal profit margins. To secure orders, many color coating enterprises have resorted to extreme measures such as extending credit terms, pre-financing, and stocking products. Unfortunately, this has also resulted in numerous companies facing bankruptcy or transferring ownership due to an inability to recover debts and maintain cash flow.
As we know, businesses exist to generate profit. To survive, many color coating companies have been forced to reduce the thickness of the coating and plating layers or compromise on paint quality, thereby gaining a price advantage in the market. However, this has led to widespread issues of fading and rusting in color steel plates within just two or three years of installation.
Color-coated steel sheets are designed to be innovative and eco-friendly building materials. Yet, due to the frequent occurrence of fading and rusting, many project owners have developed a negative perception of these materials, losing confidence in their long-term reliability.
As a member of the color coating industry, Tianwu also shares significant concerns about the industry's future. To advocate for truly high-quality, energy-efficient, and environmentally friendly materials, we have been steadfast in promoting premium-grade color-coated steel plates. Based on industry experience and our own practices, we have summarized several key factors that contribute to fading and rusting in color-coated steel sheets. We hope this summary will provide valuable insights for our customers.
Low Coating Weight
THE PLATING
The quality of the substrate coating is a crucial factor affecting the rusting of color-coated steel. According to the national standard "GB/T12754-2006 for Color Coated Steel Sheets and Strips," the hot-dip galvanized and hot-dip aluminum-zinc double-sided zinc layers of the color-coated substrates should not be less than 180g/m² and 100g/m², respectively. However, the most common color-coated substrates on the market have double-sided zinc layers of only 20-40g/m², which means the zinc layer on each side is only 10-20g/m². Users can imagine that the corrosion resistance of such substrates is significantly reduced.
Thin Coating Thickness
THE COATING
According to the national standard "GB/T12754-2006 for Color-Coated Steel Sheets and Strips," the coating thickness on the front surface of the color-coated steel should be no less than 20 microns. However, the majority of color-coated steel manufacturers in the market only apply a coating thickness of around 12-13 microns, and many in Shandong Bixing even apply coatings as thin as 8-10 microns. When observed under a 20x magnifying glass, pinhole-like areas of undercoating can be seen. Such a thin coating cannot effectively prevent moisture and air from reaching the base material, failing to protect it from rusting.
Poor Paint Quality
THE PAINTING
In order to reduce costs, color coating factories aggressively drive down the price of paint and delay payments (usually settled every two months, often via acceptance). This forces paint manufacturers to cut corners on raw materials, using lower-quality resins and color pigments. Some color coating companies even set up their own paint workshops with just a few skilled workers to produce paint in-house. Naturally, color-coated steel panels produced with unverified raw materials cannot withstand ultraviolet (UV) radiation from the sun. As a result, many of these panels start to fade and powder within two to three years, or even just a few months.
