Advantages, Disadvantages and Applications of Galvanized Pipe

Galvanized pipe (GI Pipe) generally refers to galvanized steel pipe, which is an important building material, and its advantages and disadvantages need to be considered before using galvanized pipe. Today we will talk about the advantages and disadvantages of galvanized pipe.

Advantages of galvanized steel pipe:

1. Low processing cost: the cost of hot-dip galvanizing and anti-rust is lower than that of other paint coatings. 

2. Durable and durable: hot-dip galvanized steel pipe has the characteristics of surface luster, uniform zinc layer, no missing plating, no dripping, strong adhesion and strong corrosion resistance. The anti-rust thickness can be maintained for more than 50 years without repair; in urban or offshore areas, the standard hot-dip galvanized anti-rust layer can be maintained for 20 years without repair.

3. Good reliability: the metallurgical bond between the galvanized layer and the steel material becomes a part of the steel surface, so the durability of the galvanized layer is more reliable.
4. The toughness of the coating is strong: the galvanized layer forms a special metallurgical structure, which can withstand mechanical damage during transportation and use. the
5. Comprehensive protection: every part of the plated parts can be coated with zinc, even in the depressions, sharp corners and hidden places can be fully protected.

6. Save time and effort: the galvanizing process is faster than other coating construction methods, and can avoid the time required for painting on the construction site after installation.

Disadvantages of galvanized steel pipe:

The zinc layer of cold-dip galvanized steel pipe is an electroplated layer, and the zinc layer is independently layered with the steel pipe substrate. The zinc layer is relatively thin, and the zinc layer is easily attached to the steel pipe substrate and is easy to fall off. Therefore, its corrosion resistance is poor. In newly built houses, it is forbidden to use cold-galvanized steel pipes as water supply pipes.

Although galvanized steel pipes (GI pipes) are cheap and widely used, their shortcomings will significantly affect performance and safety in long-term use.

1. Insufficient corrosion resistance

The zinc layer will gradually consume:
The galvanized layer will accelerate corrosion in humid, acidic or high-salt environments (such as coastal areas and industrial areas), eventually causing the internal carbon steel to be exposed and rusted.

Typical performance: red rust, perforation and leakage may appear after 5 to 10 years of use.
Comparison: Stainless steel pipes or PVC pipes have a longer life in the same environment.

Not suitable for corrosive media:
When transporting acidic, alkaline or chlorine-containing liquids (such as swimming pool water, chemical wastewater), the corrosion rate is extremely fast.

2. Easy to scale and clog

The zinc layer falls off to form deposits:
After long-term use of galvanized pipes, the zinc layer may peel off and accumulate in the low-lying areas of the pipe to form sediments, blocking the pipe, especially in small-diameter (DN<50mm) pipes.

Scaling problem is serious:
In hard water environment, calcium and magnesium scale is easy to form on the inner wall of the pipe, resulting in a decrease in flow (the diameter can be reduced by up to 30%), which needs to be cleaned regularly. In addition, the scale layer is easy to hide harmful substances such as bacteria and viruses, thus affecting the water quality.

Application restrictions: It is not recommended for drinking water systems (modern standards often use PPR or stainless steel pipes). For example, galvanized water pipes in old buildings often have insufficient water pressure due to blockage.

3. Welding and processing problems

Welding toxicity:
During high-temperature welding, the zinc layer evaporates to produce toxic zinc oxide fumes, which may cause "metal fume fever" for workers.
Safety requirements: Ventilation equipment and protective masks are required.

Poor welding quality:
The galvanized layer will cause pores and cracks in the weld, and the zinc layer must be polished and removed in advance, increasing construction costs.

Alternatives: It is recommended to use seamless steel pipes (such as ASTM A106) or flange connections where welding is required.

4. Bulky and inconvenient to install

Heavier than plastic pipes:
For the same pipe diameter, the weight of GI steel pipes is 3 times that of PPR pipes and 1.5 times that of stainless steel pipes. It requires more manpower to carry and install, which increases the difficulty of transportation and installation.

Backward connection method:
Depending on threaded or flange connection, the installation efficiency is much lower than the hot-melt connection of plastic pipes, and the interface is prone to leakage.

Economical efficiency: Although the material cost is low, the labor and maintenance costs may exceed plastic pipes.

5. Health and safety hazards-drinking water system

Zinc pollution risk:
Old pipes may release zinc ions, which react with chlorine in water to form zinc chloride, causing water odor (metallic taste).

Bacterial growth:
The inner wall is rough after corrosion, which is easy to breed pathogenic microorganisms such as Legionella, threatening the safety of drinking water.

6. Poor temperature adaptability

High temperature softening:
When it is in an environment >60℃ for a long time (such as a solar water heating system), the zinc layer ages faster and the strength of the steel pipe decreases.

Low temperature brittleness:
Below 0℃, the galvanized layer is prone to cracking and is not suitable for conveying frozen liquids.

Alternative materials:
High temperature: A106 GR.B seamless steel pipe
Low temperature: A333 Gr.6 low temperature steel pipe

Applicable suggestions:
Retainable scenarios: short-term temporary projects, fire protection pipelines in non-corrosive environments.
Recommended replacement scenarios: drinking water systems, HVAC, chemical pipelines, high temperature/low temperature medium transportation.

Galvanized steel pipes were once the mainstream choice in the 20th century, but in modern engineering, their performance shortcomings have prompted the industry to turn to more reliable materials.

Application of galvanized steel pipe:

1. Fire protection engineering: The current fire water supply pipes are basically galvanized pipes, and a layer of paint is applied on the outer layer of the galvanized pipes, so that everyone can see the red fire pipes, but in fact they are only galvanized. Formed by zinc pipe processing.

2. Steel structure, welding engineering: There are many shed factories outside. In the past, welded steel pipes were used to build factories. However, welded steel pipes are easy to rust. In order to prevent rust, a layer of paint should be applied. In order to solve this problem, Now many new steel structure projects directly use galvanized pipes, which can save man-hours and last longer.

3. Agriculture: It is mainly used to build warm greenhouses, flower sheds, and pillars for flowers and melons.

Storage method of galvanized pipe:

The site or warehouse where the galvanized steel pipe is placed should be selected in a clean and well-drained place, away from factories and mines that produce harmful gases or dust. Weeds and all debris should be removed on the site, and the galvanized steel pipe should be kept clean. Do not stack together with acid, alkali, salt, cement and other corrosive materials in the warehouse. Square tubes of different varieties should be stacked separately to prevent confusion and contact corrosion. Large steel sections, rails, steel plates, large-diameter steel pipes, forgings, etc. can be stacked in the open air.

Some small square tubes, thin steel plates, steel strips, silicon steel sheets, small-diameter or thin-walled seamless steel pipes, various cold-rolled and galvanized steel pipes, and high-priced, easily-corroded metal products can be stored in the warehouse. The warehouse should be selected according to the geographical conditions. Generally, an ordinary closed warehouse is used, that is, a warehouse with a roof, a wall, tight doors and windows, and a ventilation device.

Read more: What are the Advantages of Stainless Steel Water Pipes over Galvanized Water Pipes?