What are the main methods of galvanization?

Hot-dip galvanizing involves immersing steel or iron articles into a bath of molten zinc at temperatures typically between 815°F (435°C) and 850°F (455°C). The zinc reacts with the surface of the metal, forming a series of zinc-iron alloy layers. Hot-dip galvanizing provides a thick and durable coating, making it suitable for outdoor applications, such as structural steel, fences, and guardrails.

Hot-dip galvanizing, due to its thick and durable zinc coating, offers excellent corrosion resistance with a typical lifespan of 50 to 100 years. This makes hot-dip galvanized steel a cost-effective choice for long-term applications, reducing maintenance and replacement costs. It is considered an environmentally-friendly process as it utilizes zinc, a natural and recyclable material, and requires minimal energy compared to other corrosion protection methods.

Hot-dip galvanizing does produce a relatively thick coating, which may not be suitable for applications requiring a thin decorative finish. Its typical appearance is shiny and spangled, which may not be visually appealing for certain architectural or aesthetic applications.

Indeed, in summary, hot-dip galvanizing offers excellent long-term corrosion protection and durability, making it a preferred choice for various applications, especially in outdoor and harsh environments.

The finish of hot dipped galvanized coating can vary based on several factors, including the cooling and solidification process of the molten zinc during galvanization and any subsequent treatments or processes applied to the coated steel. Here are some common types of galvanized coating finishes: Standard Spangle, Large Spangle, Small Spangle, Zero(no) Spangle and Bright Spangle.

Electro-galvanizing involves applying a zinc coating to steel or iron through an electroplating process. The material is immersed in an electrolyte solution, and an electric current is passed through the solution to deposit a layer of zinc onto the metal surface. Electro-galvanizing is typically used for smaller and more intricate parts, and it results in thinner coatings compared to hot-dip galvanizing.

Electro-galvanizing allows for precise control over the thickness of the zinc coating, and the coatings typically have a smoother and more uniform appearance compared to hot-dip galvanized coatings. The thinner and more flexible nature of electro-galvanized coatings is advantageous for applications where post-galvanizing forming or bending of the coated steel is required.

On the other hand, the thinner nature of electro-galvanized coatings may result in reduced corrosion protection compared to hot-dip galvanizing. The thinner coating makes electro-galvanized steel more susceptible to mechanical damage during handling, transportation, or installation, potentially exposing the underlying steel to corrosion.

In conclusion, electro-galvanizing is a suitable method for providing controlled and precise zinc coatings on smaller parts with specific requirements such as improved aesthetics or increased formability. However, its thinner coating and limited corrosion protection make it less suitable for heavy-duty outdoor applications or environments where high corrosion resistance is essential.

Metal in China® (XINTUOYUAN) is a China galvanized steel sheet manufacturer with rich experience and advanced galvanized production lines. Over the years, advancements in galvanizing technology improved the efficiency and quality of the galvanizing process. Innovations in zinc metallurgy and coating techniques allowed for better control of the coating thickness and quality, making galvanized steel more reliable and cost-effective.

Sherardizing, also known as diffusion galvanizing, is a method where steel or iron articles are placed in a sealed container containing zinc powder. The container is then heated to a temperature below the melting point of zinc (typically around 750°F or 400°C). The zinc evaporates and diffuses onto the metal surface, forming a zinc-iron alloy coating. This process is commonly used for small parts, fasteners, and threaded components.

Sherardizing is a low-temperature process that significantly reduces the risk of hydrogen embrittlement in high-strength steels. It can provide a uniform and consistent coating thickness even on complex shapes and surfaces with different geometries. The Sherardized coating forms a metallurgical bond with the steel substrate, ensuring excellent adhesion and increased durability.

Unlike some other galvanizing methods, the Sherardizing process is slower and requires longer processing times. Compared to hot-dip galvanizing, Sherardizing typically results in thinner coatings. While it offers good corrosion protection, it may not be as durable in harsh or corrosive environments.

In summary, Sherardizing provides a uniform, corrosion-resistant, and well-adhered coating, making it a suitable choice for small parts and fasteners. However, its limitations in coating thickness and color options may make it less suitable for applications requiring thicker or visually appealing coatings.

Mechanical galvanizing is a process that involves tumbling steel or iron articles with a mixture of zinc powder, special glass beads, and proprietary chemicals. The friction generated during the tumbling process causes the zinc and coating chemicals to bond with the metal surface. This method is commonly used for smaller parts, screws, and fasteners.

Mechanical galvanizing provides a uniform zinc coating on the surface of steel components, and the zinc coating enhances lubricity, making it suitable for threaded components and fasteners that require reduced friction during assembly. Mechanical galvanizing is a cold process, meaning it does not subject the steel parts to high temperatures, minimizing the risk of deformation or warping.

However, mechanical galvanized coatings are thinner and have limited corrosion resistance. The process requires high surface preparation standards, and the adhesion may be lower compared to some other galvanization methods.

In conclusion, mechanical galvanizing offers a uniform zinc coating, improved lubricity, and reduced risk of hydrogen embrittlement. However, its thinner coating and limited corrosion resistance may make it less suitable for applications that require high levels of protection in harsh or corrosive environments.

Each galvanization method has its advantages and is suitable for specific applications. The choice of method depends on various factors, such as the size and shape of the articles, the required coating thickness, the desired appearance, and the expected environmental conditions for the coated products.

Metal in China(HUA ZHU) Co., Ltd., established in 1999, is a leading manufacturer and supplier dedicated to carbon steel,  galvanized steel and stainless steel materials and products. We provide many overall metal solutions for customers from all walks of life at home and abroad, such as military equipment suppliers, design agencies, construction contractors, metal product distributors, elevator manufacturers, and home appliance manufacturers.