Things you need to know about hot dipped galvanized pipe

Galvanized pipe mainly used in transmission of coal gas, steam. IBC (Tianjin) Industrial Co.,Ltd could manufacture all sizes of galvanized steel pipes. So as other welded pipes, such as ERW, LSAW, SSAW. And if you want to manufacture it by yourself, you could also contact with us, we could supply whole set of producing and testing machines. And firstly, lets see what is galvanized pipe below?

galvanized pipe

What is galvanized pipe?

Galvanized steel pipe is the carbon steel pipes that are coated with a protective layer of zinc. The zinc layer served as a sacrificial layer, it will get rust before the carbon steel under neath it. Galvanized steel pipes include Two types: hot dipped galvanized steel pipes and cold galvanized steel pipes. Galvanized layer will strengthen the anti-corrosion performances of steel pipe. Pipe could use many types of coating, why use zinc? Let’s see it below:

Why use zinc as the coated layer?

There are many kinds of coating for steel pipes. So why use zinc as this coating? That’s because of zinc element is active than steel element. On one hand, zinc oxide of galvanized steel pipe surface is compact, it can stop oxidation(corrosion). On the other hand, when electric-chemical corrosion has occurred, the first kind of metal corrupted is zinc rather than steel. The zinc layer effect is stop corrosion speed, and prolong the life of steel pipe.

Galvanized steel pipes sizes and specifications

  • Nominal diameter (inch): 1/2~4
  • Nominal wall thickness (mm): 2.0~4.5
  • Test pressure index: Diameter: 10.2~168.3 mm 3 MPa
  • Diameter: 177.8~323.9 mm 5 MPa

Types of Galvanized steel pipes

Galvanized steel pipes include two kinds: (1) Hot dipped galvanized pipe and (2) Cold galvanized pipes, also called electric galvanized pipes. Below, let’s show more information about these two kinds of GI pipe. Including the brief introduction, and manufacturing process, and the zinc thickness for GI pipes. Firstly, we see the hot dipped galvanized pipe.

Introduction of Hot dipped galvanized steel pipes

Hot dipped galvanized steel pipe is in manufacturing process using steel pipes of removed rust dipped into zinc liquid of 500℃ temperatures, and making steel surface attached zinc layer so as to achieve the purpose of anti-corrosion.

Hot galvanizing is a kind of effective anti-corrosive treatment, used in kinds of steel structural products. Since 1836 France used hot galvanizing in industry the first time, it have been more than 180 years. However following by the development of cold rolled steel, it has greatly developed in recent decades. With the high-voltage transmission, transportation, communications, the protection products require higher standards, hot galvanizing demand is also increasing.

The processing of hot galvanizing:

Firstly, Finished pickling; Then, washing; After plating, we will be drying and hanging plating. We use cooling and medicine, then cleaning and at last grinding. Till now, the hot galvanized finished.
Zinc thickness for hot galvanized steel pipe

Hot galvanized steel pipe zinc layer thickness is 35μm, and the most thick is up 650μm. Instead cold zinc layer thickness is only 5-15μm. Zinc layer have the effects of anti air corrosion and electric chemical protection.

galvanized pipe-1

The theory of hot galvanized steel pipe’s zinc layer effect to anti corrosion. In the processing of hot galvanizing, it will formed a film of zinc-steel alloy layer first, above it is pure zinc layer. When the air corroded the zinc layer, it will form a layer of ZnO, Zn(OH)2 and basic zinc carbonate protection film. Which have the effect of anti air corrosion. When this film was destroyed, a new one will form. When the zinc layer destroyed heavily, zinc start up electric chemical protection.

Zinc as the first element dissolved. It’s obviously that hot galvanized steel have better anti corrosive performances than cold galvanizing pipes.

How long of hot galvanized steel pipes lifetime?

Galvanized steel pipe mainly used in transmission of coal gas, steam. It was used as water pipe, but after several years past, there were many rust in the pipe, and water get yellow color for carrying iron oxide. The water not only polluted dishes or other sanitary ware, but also carrying bacteria produced in the internal surface which not smooth . As a result of the corrosion, the water contains heavy metal element is too much and is harmful to people’s health. For this reason, developed countries gradually banned it using as water pipe since 1960s.

Galvanized steel pipe have long lifetime. But in different conditions the lifetime of use are different. Generally speaking, 13 years in heavy industrial district, 50 years for ocean environment, 104 years in suburbs, 30 years in city. In fact galvanizing have played a role of anti- rusty, it is no need other rust treatment.

Hot galvanizing process specially suitable for kinds of strong-acid, alkali fog and other strong corrosive conditions. This kinds of fastener used a lot in outside of steel tower contribution.

After knowing the hot dipped galvanizing pipes, we will see the cold one. They are different.

Brief Introduction Cold Galvanized Pipe

Cold galvanized steel pipe is using electric chemical processing coated zinc layer on steel pipe. The zinc layer usually 20~30μm thick.

Cold Galvanized Steel Pipes Manufacturing Process

Degreasing – electroplating – passivation – drying – packaging

Zinc Thickness for Cold Galvanized Steel Pipe

Cold GI pipes zinc thickness is 5-15 μm, the layer is dense, and there is no inclusion with organic matter.

Cold Galvanization Technology is no Longer Recommend for Pipe products. For more thinner zinc layer reason, countries of the world have gradually forbidding the cold galvanized steel pipes as water pipe and coal gas pipes. But due to cold galvanizing processing have smooth appearance of surface, it always used in manufacturing small pieces which requiring precise plating. Such as screws, Machinery manufacturing, electronics, precision instruments, chemicals, light industry, transportation, weapons, aerospace, atomic energy, etc., in the national economy has great significance.

I think you will knowing the things about galvanized steel pipes after reading this paragraph. And if you want to learn more about the galvanized pipe, you could contact with us for more information. IBC (Tianjin) Industrial Co.,Ltd could supply all kinds of pipe for your projects. Not only pipe, but also pipe fittings and other steel accessories for you.