Comparison of Hot-Dip Galvanized and Pre-Galvanized Pipes

1. What is hot-dip galvanized pipe?

Hot-dip galvanized pipe is galvanized by immersing the processed steel pipe in a high-temperature zinc liquid of about 450°C. This process forms a dense, solid zinc-iron alloy layer and a pure zinc layer on the surface of the steel pipe, which has extremely high adhesion and corrosion resistance.
Features:
The zinc layer has a high thickness: it can generally reach 45~80 microns (μm), and it can still maintain a long service life in harsh environments.
Strong anti-corrosion performance: the zinc layer not only forms a physical barrier, but also prevents steel from being corroded through "cathodic protection" when it is locally damaged.
Long service life: up to 2050 in general environments, and 1020 years in industrial and high-salt environments.
Wide range of applications: including outdoor building structures, communication towers, traffic guardrails, water conservancy facilities, photovoltaic brackets, etc.
Due to its excellent durability, hot-dip galvanized pipes are considered a more reliable choice in long-term engineering projects, especially suitable for use in harsh environments such as wind, sun, rain and corrosion.

2. What is a pre-galvanized pipe?

Pre-galvanizing is also called mill galvanizing. This process is very close to hot-dip galvanizing, but is carried out in the first stage of production. It always takes place in the steel mill on materials that are already in a specific shape or before being cut to size and processed.Pre-galvanizing includes some of the steps of hot-dip galvanizing, such as cleaning the surface, immersion in a hot zinc bath, and the coiling process.

3.Comparison of Hot-Dip Galvanized and Pre-Galvanized Pipes

The main difference between hot-dip galvanized and pre-galvanized pipes is the thickness of the zinc coating on the steel pipes. Hot-dip galvanized pipes have a more robust zinc coating, making them more expensive than pre-galvanized pipes. However, they offer reliable protection against rust and other types of corrosion, making them ideal for outdoor applications, especially in industrial and harsh environments.

In contrast, pre-galvanized pipes have a thinner, more delicate coating than hot-dip pipes, making them less expensive. They are ideal for indoor applications or areas with low environmental hazards.

Comparison Aspect	Hot-Dip Galvanized Pipe	Pre-Galvanized Pipe
Galvanizing Method	The finished steel pipe is dipped into molten zinc.	Zinc is applied to the steel strip before pipe forming.
Zinc Coating Thickness	Thicker (typically 45–80μm or more)	Thinner (typically 10–30μm)
Adhesion	Strong metallurgical bond; coating does not peel easily	Weaker adhesion; cut edges and welds may lack zinc layer
Corrosion Resistance	Excellent, suitable for harsh environments	Moderate, suitable for low-corrosion environments
Service Life	20–50 years depending on the environment	5–10 years depending on the environment
Cost	Higher due to more complex process	Lower cost, suitable for mass production
Appearance	Rougher or matte finish, darker gray surface	Smooth and shiny metallic surface
Typical Applications	Outdoor structures, industrial pipelines, utility projects	Indoor framing, cable trays, greenhouses, light structures

What is the difference between galvanized pipe and black steel pipe

The main difference between galvanized pipe and black steel pipe is the surface treatment and corrosion resistance. The surface of galvanized pipe is covered with a layer of zinc, which makes it more corrosion-resistant, while black steel pipe has not been additionally treated and is prone to rust. Galvanized pipe is usually used to transport water, while black steel pipe is more suitable for transporting gases, such as natural gas.