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Hot-Dip Galvanizing(HDG)
Introduction to Hot-Dip Galvanizing
Hot-dip galvanizing (HDG) is one of the most common galvanizing methods. The process involves completely immersing iron or steel in molten zinc. Compared to electro-galvanizing, hot-dip galvanizing has the advantage of relatively lower cost.
The chemical reactions during galvanizing only occur on clean iron or steel surfaces. Therefore, before hot-dip galvanizing, steel materials undergo degreasing (using alkaline chemicals to remove oil), washing, and pickling to ensure the quality of the finished product. Afterward, the steel materials are immersed in a flux (the main components of which are usually ammonium chloride and zinc chloride) and preheated. Once treated, the steel materials are immersed in molten zinc (i.e., melted zinc), where a series of complex chemical reactions occur between the iron and zinc, producing iron-zinc metal compounds, thus forming a zinc layer on the iron surface. The processes following hot-dip galvanizing include cooling and checking the thickness of the zinc coating.
Adding other metals to the molten zinc can adjust the properties of the zinc layer: for example, adding metals such as aluminum, magnesium, and nickel can improve the corrosion resistance of the zinc layer, while adding metals such as aluminum, lead, tin, and antimony can optimize the appearance of the zinc layer. On the other hand, the carbon, silicon, manganese, phosphorus, and sulfur content in the steel materials all affect the structure and properties of the zinc layer.
The principle of rust prevention: During hot-dip galvanizing, the zinc reacts chemically with the iron, causing the zinc layer to bond tightly with the iron, isolating the iron from oxygen and water, forming a series of alloy layers. A dense film of zinc oxide forms on the zinc coating. Zinc oxide is poorly soluble in water, thus protecting the iron from rusting. Furthermore, the zinc layer has a unique metallic structure, making it a very hard coating with excellent wear resistance.
Applications: Zinc plating is a common rust prevention method. Steel materials of varying sizes (e.g., small mechanical parts like bolts, to large structural components) and shapes (e.g., hollow objects, complex shapes, utensils, etc.) can be galvanized. "White iron" specifically refers to galvanized iron, widely used in petrochemical, telecommunications, transportation, construction, machinery, and agriculture industries. The following table lists hot-dip galvanizing applications:
What is "Zinc Plating"?
Zinc plating refers to the rust-prevention method of coating the surface of iron or steel with metallic zinc. Zinc is a highly corrosion-resistant metal that can isolate iron from oxygen and water, preventing the chemical reactions required for rusting. Because zinc is more reactive than iron, even if the zinc plating is damaged, it can still prevent rusting through sacrificial electrochemical protection. The main galvanizing methods are hot-dip galvanizing (HDG), electro-galvanizing (EG), and cold galvanizing.Hot-dip galvanizing (HDG) is one of the most common galvanizing methods. The process involves completely immersing iron or steel in molten zinc. Compared to electro-galvanizing, hot-dip galvanizing has the advantage of relatively lower cost.
The chemical reactions during galvanizing only occur on clean iron or steel surfaces. Therefore, before hot-dip galvanizing, steel materials undergo degreasing (using alkaline chemicals to remove oil), washing, and pickling to ensure the quality of the finished product. Afterward, the steel materials are immersed in a flux (the main components of which are usually ammonium chloride and zinc chloride) and preheated. Once treated, the steel materials are immersed in molten zinc (i.e., melted zinc), where a series of complex chemical reactions occur between the iron and zinc, producing iron-zinc metal compounds, thus forming a zinc layer on the iron surface. The processes following hot-dip galvanizing include cooling and checking the thickness of the zinc coating.
Adding other metals to the molten zinc can adjust the properties of the zinc layer: for example, adding metals such as aluminum, magnesium, and nickel can improve the corrosion resistance of the zinc layer, while adding metals such as aluminum, lead, tin, and antimony can optimize the appearance of the zinc layer. On the other hand, the carbon, silicon, manganese, phosphorus, and sulfur content in the steel materials all affect the structure and properties of the zinc layer.
The principle of rust prevention: During hot-dip galvanizing, the zinc reacts chemically with the iron, causing the zinc layer to bond tightly with the iron, isolating the iron from oxygen and water, forming a series of alloy layers. A dense film of zinc oxide forms on the zinc coating. Zinc oxide is poorly soluble in water, thus protecting the iron from rusting. Furthermore, the zinc layer has a unique metallic structure, making it a very hard coating with excellent wear resistance.
Applications: Zinc plating is a common rust prevention method. Steel materials of varying sizes (e.g., small mechanical parts like bolts, to large structural components) and shapes (e.g., hollow objects, complex shapes, utensils, etc.) can be galvanized. "White iron" specifically refers to galvanized iron, widely used in petrochemical, telecommunications, transportation, construction, machinery, and agriculture industries. The following table lists hot-dip galvanizing applications:
| Industrial Applications | Examples of Uses |
| Petrochemical Industry | Oil pipelines, oil well pipes, oil processing equipment, oil storage containers, condensers |
| Telecommunications | Radio masts and towers, communication cables, power towers, substations |
| Transportation | Highway guardrails, highway or railway safety nets, railway noise barriers, windbreaks, snow barriers, road signs, streetlights |
| Construction | Factory steel structure, drainage pipes, plumbing equipment, electrical conduit, bridge structure |
| Machinery | Electric motor housing, ventilation device housing |
| Agriculture | Greenhouses, greenhouse frames, planting bed frames, agricultural water troughs |
| Solar energy | Photovoltaic rail supports |