MS vs GI Pipe: Differences, Full Form & Which to Choose?

MS pipe stands for Mild Steel pipe (low-carbon steel). GI pipe stands for Galvanized Iron pipe (steel pipe coated with zinc). This article will compare MS pipes and GI pipes in terms of material properties, manufacturing processes, costs, and applications to help you choose the appropriate piping for your project.

MS vs GI Pipe: Quick Comparison

Feature	MS Pipe (Mild Steel)	GI Pipe (Galvanized Iron)
Full Form	Mild Steel	Galvanized Iron
Material	Low-carbon steel (≤0.25% carbon)	Steel pipe coated with zinc
Corrosion Resistance	Low (rusts easily)	High (zinc coating protects against rust)
Strength	High strength and wear resistance	Good strength, but zinc coating can be damaged
Surface Appearance	Dark gray/black, dull	Silver-white/light gray with visible zinc spangles
Cost	Lower	Higher (due to galvanizing process)
Applications	Structural, mechanical, oil/gas	Water supply, fire protection, outdoor piping

What is MS Pipe?

MS Pipe (mild steel pipe) refers to the content of less than 0.25% carbon steel because of its low strength, low hardness and soft. It includes most of the part of ordinary carbon steel and high-quality carbon structural steel, mostly without heat treatment used in engineering structures, some carburizing heat treatment and other mechanical parts required for wear.

Mild Steel is untreated and usually hot or cold rolled or in the case of pipe extruded while molten. Low carbon content and rusts in humid weather and can be bent easier than other steel. Its not black pipe used for gas, its not case hardened with cyanide, its not galvanized with zinc plating, its not blued like used for guns, its not cast like for cast iron furniture. Its the most affordable type of steel.

What is GI Pipe?

GI Pipe is “Galvanized Iron” Pipe. Material MS is mild steel and GI is galvanized steel that has been hot dipped. These days the pipe will likely be made from steel rather than iron. Galvanized iron pipes commonly used on water pipe lines, it is dipped into zinc for corrosion protection.

Detailed Comparison: MS Pipe (Mild steel)  vs GI Pipe (Galvanized iron) 

Although galvanized steel pipes and mild steel pipes (carbon steel pipes) both belong to the category of steel pipes, their materials and uses are quite different. 

1. Material Properties

MS Pipe: Mild steel pipe has a carbon content of less than 0.25%. It has good strength, high malleability, and is easy to weld. However, it has low corrosion resistance and will rust when exposed to moisture. It is commonly used in structural applications, machinery parts, and general fabrication.

GI Pipe: Galvanized iron pipe is steel pipe coated with a layer of zinc through a hot-dip or electroplating process. The zinc coating provides excellent corrosion resistance, making it suitable for outdoor and water applications. The base steel provides the necessary mechanical strength.

2. Manufacturing Process

MS Pipe: The manufacturing of mild steel pipes includes perforating steel ingots or solid round steel to form capillary tubes, which are then hot-cold rolled and cold-drawn. This process occupies a key position in the domestic steel pipe field.

GI Pipe: The manufacture of galvanized steel pipe involves coating the pipe with a layer of zinc through a process such as hot-dip plating or electroplating, which can improve the pipe's corrosion resistance and durability but can also distort the pipe's size and shape.

3. Surface Coating & Appearance

The most visible difference between MS and GI pipes is their surface finish.

MS Pipe: MS pipes have a dark gray or black appearance with no metallic luster, often covered with mill scale or oil from the manufacturing process.

GI Pipe: GI pipes have a bright silver-white or light gray finish with a distinctive metallic sheen, often featuring visible zinc spangles (crystals). The zinc coating is typically 40-200μm thick for hot-dip galvanizing, which provides the primary corrosion protection. However, if the coating is scratched or damaged, the underlying steel will be exposed and prone to rusting.

4. Weldability & Workability

MS Pipe: MS pipes offer excellent weldability due to their low carbon content, making them easy to weld without special procedures. They also have good workability and can be easily bent, cut, and formed into complex shapes.

GI Pipe: GI pipes present challenges in both welding and forming.

● Welding: The zinc coating vaporizes at welding temperatures, producing toxic fumes and requiring proper ventilation. The weld area also loses its corrosion protection and must be re-coated with zinc-rich paint.
● Workability: The zinc layer can crack or peel during bending or stamping, so larger bend radii or special tools may be required to avoid damaging the coating.

5. Cost

MS Pipe: The production process of mild steel pipes is relatively simple and the cost is low.
GI Pipe: The production process of galvanized steel pipe is more complicated and requires galvanizing treatment, so the cost is higher.

6. Application scope

MS Pipe: Mild steel pipes are widely used in petroleum, chemical, natural gas and construction industries due to their high strength and excellent quality characteristics.

GI Pipe: Galvanized steel pipes are mainly used in water supply, fire protection, aviation and other fields because of their good corrosion resistance.

Expand Information: Hot-Dip vs Cold-Dip Galvanizing

Galvanized steel pipes are divided into cold-dip galvanized steel pipes and hot-dip galvanized steel pipes. Cold-dip galvanized steel pipes have been banned, and the latter has been advocated by the country for temporary use.

Hot-dip galvanized pipe:

Hot-dip galvanized pipe reacts molten metal with an iron matrix to produce an alloy layer, thereby combining the matrix and the coating. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned in an aqueous solution of ammonium chloride or zinc chloride or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to in a hot dip plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The hot-dip galvanized steel pipe matrix undergoes complex physical and chemical reactions with the molten plating bath to form a corrosion-resistant zinc-iron alloy layer with a tight structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix, so it has strong corrosion resistance.

Cold-dip galvanized pipe:

Cold-dip galvanized pipe is electro-galvanized. The amount of galvanizing is very small, only 10-50g/m2. Its corrosion resistance is much worse than that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, most do not use electro-galvanizing (cold plating). Only small businesses with small scale and old equipment use electro-galvanizing, and of course their prices are relatively cheaper. The Ministry of Construction has officially announced that cold-galvanized pipes with backward technology will be phased out and cold-galvanized pipes are not allowed to be used as water and gas pipes. The zinc layer of cold-dip galvanized steel pipe is an electroplated layer, and the zinc layer is layered independently from the steel pipe matrix. The zinc layer is thin, and the zinc layer simply adheres to the steel pipe matrix and falls off easily. Therefore, its corrosion resistance is poor. In new residential buildings, it is prohibited to use cold-dip galvanized steel pipes as water supply pipes.

Applications of Galvanized Steel Pipes:

Galvanized steel pipe is a seamless & welded steel pipe with a hot-dip or electroplated zinc layer on the surface. Galvanizing can increase the corrosion resistance of steel pipes and extend their service life. Galvanized pipes are widely used. In addition to being used as pipeline pipes for general low-pressure fluids such as water, gas, and oil, they are also used as oil well pipes and oil pipelines in the petroleum industry, especially offshore oil fields, and as oil heaters and condensators in chemical coking equipment. Pipes for coolers, coal distillate wash oil exchangers, pipes for trestle pipe piles, and support frames for mine tunnels, etc.

Hot-dip galvanized steel pipes are widely used in construction, machinery, coal mines, chemical industry, electric power, railway vehicles, automobile industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, prospecting machinery, greenhouse construction and other manufacturing industries.

Frequently Asked Questions:

Q1: What is the full form of MS pipe?
A: MS stands for Mild Steel.

Q2: What is the full form of GI pipe?
A: GI stands for Galvanized Iron.

Q3: What is the main difference between MS and GI pipe?
A: The core difference is corrosion resistance. GI pipe has a zinc coating to prevent rust, while MS pipe does not and is prone to corrosion.

Q4: Which is more expensive, MS or GI pipe?
A: GI pipe is more expensive due to the additional galvanizing process.

Q5: Can GI pipe be used for drinking water?
A: Yes, GI pipes are commonly used for water supply lines. However, in some regions, plastic or stainless steel is preferred for new construction due to concerns about zinc leaching.

Q6: How can I visually tell MS and GI pipes apart?
A: MS pipes have a dark gray/black, dull surface. GI pipes have a bright, silver-white, shiny surface with visible zinc crystals (spangles).

Q7: Can I weld GI pipe easily?
A: Welding GI pipe is more difficult. The zinc coating vaporizes at welding temperatures, producing fumes and leaving the weld area unprotected. The zinc must be removed before welding, and the welded area must be re-coated afterward.

Conclusion: 

Choosing between MS and GI pipe depends on your specific application. MS pipe is suitable for structural and general fabrication where corrosion is not a primary concern. GI pipe is the better choice for outdoor, water, and corrosive environments where long-term protection is required. Evaluate your project's requirements to make the right decision.

Related Resources:
● Carbon Steel vs Black Steel: Key Differences
● Schedule 40 vs Schedule 80 Pipe: A Selection Guide
● Seamless vs Welded Pipe: Process, Performance & Cost

● Guide for Selecting the Thickness of Galvanized Steel Pipe

Additional Information: GI Pipe Terminology

Are galvanized steel pipes and galvanized iron pipes the same thing?

1. Mixed terminology: In most cases, the two are interchangeable, but attention should be paid to specific standards (for example, when the contract or drawing states "GIP", it is necessary to confirm whether it specifically refers to a certain type of galvanized pipe).
2. Historical legacy: The "galvanized iron pipe" in old buildings may be made of wrought iron (good ductility but low strength), which has been basically replaced by steel in modern times.

3. Regional differences: China often calls it "Galvanized steel pipe", while North American plumbers may be more familiar with "Galvanized Iron Pipe".

Need Help Choosing the Right Pipe?

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