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Galvanized coil is a metal material produced through a continuous galvanizing process, in which a zinc layer is adhered to the surface of thin steel sheets. Its primary materials are steel and zinc alloy, and it is categorized into two types: ordinary galvanized steel sheets and alloyed galvanized steel sheets. China is the world's largest producer of hot-dip galvanized coil, with a production volume consistently maintained at around 90 million tons [3]. Galvanized sheets are primarily used in the construction industry, home appliances, automobile manufacturing, and light industry [4]. As the market penetration of new energy vehicles increases, the demand for galvanized sheets has significantly grown, accounting for 11.58% of the demand in October 2025 [5]. The production process involves immersing the coiled steel sheets in a molten zinc bath, and after exiting the bath, the alloyed treatment requires heating to 500°C to form a zinc-iron alloy layer. This process offers advantages in paint adhesion and weldability. During production, technologies such as slag-dredging robots and zinc layer thickness measuring instruments are employed to ensure product quality
The products are divided into seven levels based on performance, including general purpose, mechanical engagement, stamping, etc. The base plate is made of cold-rolled coil or hot-rolled pickled coil. The coating is divided into four categories based on the zinc flake structure: normal zinc flake, small zinc flake, no zinc flake, and zinc-iron alloy. It is also divided into codes ranging from Z60 to Z600 based on the weight of the double-sided coating. Surface treatment includes processes such as passivation, oiling, paint sealing, and phosphating. The main defects include coating peeling, white rust, black spots, and mechanical damage. In 2025, the total production capacity of galvanized coil sample enterprises was 127 million tons, with an annual output of 71.9489 million tons. In terms of exports, the total export volume of galvanized sheets (strips) in 2025 is expected to exceed 20 million tons [8]. In the market, as of mid-February 2026, the price of galvanized coil in the mainstream market fluctuates within a certain range, with total inventory at its highest level in the past four years during the same period of the lunar calendar. The demand side shows a slow recovery trend
Hot dip galvanizing remains the most widely used and effective process measure for corrosion protection of steel. The basic process involves immersing coiled steel sheets into a molten zinc bath, allowing a layer of zinc to adhere to its surface [4].
With technological advancements, the automation level of galvanizing production lines continues to improve. For instance, the application of slag-scooping robots enables efficient removal of zinc pot dross 24 hours a day, ensuring product quality. The use of zinc layer thickness measuring instruments allows for zero-time-lag dynamic adjustment, enabling precise control over zinc layer thickness. Furthermore, new production line technologies are also evolving, such as the wide-plate zinc-aluminum-magnesium production line fueled by blast furnace gas, which can be used to produce high-end products such as photovoltaic supports
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