Get to Know Galvanizing: What It Is and Why Steel Needs Zinc Coating

Galvanizing (Hot Dip Galvanizing or Zinc Coating) is one of the most reliable methods to protect steel from rust and corrosion. When steel is exposed to moisture and oxygen, rust will gradually eat away the metal surface, leading to serious damage and structural failure. For construction projects, buildings, and infrastructure, this hidden damage can be extremely dangerous, since the condition of the embedded steel is often invisible.

Applying a zinc coating through galvanizing helps prevent rust formation and significantly extends the lifespan of steel—often lasting over 70 years even in harsh environments. This makes galvanizing a cost-effective and long-term solution for both industrial and construction applications.

Learn more: Why you should galvanize steel before use?

Types of Galvanizing Methods

Today, there are several galvanizing processes designed for different applications, including:

• Hot Dip Galvanizing (HDG) – immersing steel in molten zinc at 450°C.

• Continuous Hot Dip Galvanizing – used for steel sheets and coils in a continuous process.

• Centrifuge Galvanizing (Spinning) – ideal for small parts like bolts, nuts, and fasteners.

• Electro-galvanizing – zinc coating using electric current, producing smooth and thin layers.

• Mechanical Coatings – zinc particles mechanically bonded to steel.

• Zinc Spraying (Thermal Spray Coating) – spraying molten zinc onto steel surfaces.

• Zinc-Rich Paints – protective coating containing high zinc content.

• Sherardizing – a diffusion process of zinc into steel at high temperature.

Among these, Hot Dip Galvanizing (HDG) is the most widely used due to its durability, cost efficiency, and suitability for various steel shapes and sizes.

Standard Hot Dip Galvanizing Process: 8 Key Steps

To meet international galvanizing standards (ASTM, BS, JIS), the galvanizing process must go through these steps:

• Degreasing – removing oil, grease, and dirt with alkaline or solvent solutions, followed by water rinsing.

• Pickling – immersing steel in hydrochloric acid to remove rust, mill scale, and oxides, then rinsed with clean water.

• Flux Solution – dipping the steel into zinc ammonium chloride to prevent oxidation and improve bonding between zinc and steel.

• Drying – preheating and drying to remove moisture before immersion.

• Zinc bath (Hot Dip Galvanizing) – immersing the steel into molten zinc at ~450°C, forming a metallurgical zinc-iron alloy layer.

• Quenching – cooling in water to stabilize the coating and improve handling.

• Anti-white rust treatment – surface treatment to slow down white rust during storage and transportation.

• Inspection & Quality Control – checking coating thickness, adhesion, and visual inspection according to ASTM, BS, or JIS standards.

Siam Steel Galvanizing (SSG): Thailand’s Leading Hot Dip Galvanizing Service

With over 35 years of experience and the largest hot dip galvanizing capacity in Thailand, Siam Steel Galvanizing (SSG) is committed to delivering high-quality galvanized steel coating services that meet international standards.

Our three galvanizing plants are ISO-certified and designed to support infrastructure, energy, construction, and manufacturing industries nationwide. With advanced technology, strict quality control, and sustainable practices, we are a trusted partner for businesses that require durable, anti-rust steel solutions.

If you are unsure whether galvanizing is suitable for your project, you can contact us for free consultation:

Phone : (+66) 02-705-8755
E-mail: ssgl@ssggalvanizing.com
Official Line: @ssggalvanizing (or click to add @LINE)

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