Differences Between GI Pipe and GP Pipe: Complete Analysis of Selection, Performance and Cost

NEWS&CASES

Time：2026-05-25

Class：Blog

In construction, water supply and drainage, steel structure and foreign trade procurement, GI pipes and GP pipes are frequently confused. However, they have obvious discrepancies in manufacturing process, zinc coating thickness, pressure resistance, service life and application scenarios. Improper pipe selection will lead to premature rusting, pipeline leakage, higher maintenance cost and even project rework.

This article analyzes the core differences between GI and GP pipes from technical parameters, application scope, cost comparison and purchasing guidance. It helps buyers make accurate selection, reduce operational risks and control project budget.

Basic Definition & Manufacturing Process

GI Pipe (Galvanized Iron Pipe)

Manufacturing process: Steel pipes are formed first, then fully immersed in molten zinc liquid at around 450℃ for hot-dip galvanization. The zinc layer forms metallurgical bonding with steel substrate with strong adhesion.

Common standards: ASTM A53, BS EN 10240, IS 1239

GP Pipe (Pre-Galvanized Plain Pipe)

Manufacturing process: Steel coils are electro-galvanized at normal temperature before being rolled and welded into pipes. The zinc layer only attaches physically with thin and uniform thickness.

Common standards: EN 10346 DX51D, JIS G3302

Core distinction: GI pipe is galvanized after pipe forming with thick and firm zinc coating. GP pipe is galvanized before forming with thin zinc layer that peels off easily.

2. Technical Parameter Comparison

Parameter	GI Pipe	GP Pipe	Practical Impact
Zinc Coating Thickness	60–85 μm (360–480 GSM)	15–25 μm (120–180 GSM)	GI owns 3-4 times longer anti-rust lifespan
Wall Thickness	3–4mm heavy duty	1–2mm light duty	Determines structural strength and pressure bearing capacity
Working Pressure	1.6–2.5 MPa high pressure	≤1.0 MPa low pressure	Suitable for fire control and normal indoor pipelines respectively
Service Life	20–50 years outdoor & underground	5–15 years indoor dry environment	GP tends to rust and perforate within 5 years outdoors
Unit Weight	Heavy	Light	GP cuts down transportation and installation cost
Surface Appearance	Dark grey, rough with zinc spangle	Bright and smooth	GP fits decorative visible structures
Market Price	30%-50% higher	Economical choice	Cost-effective for short-term budget projects

3. Suitable Application Scenarios

GI Pipe: Heavy anti-corrosion, high pressure and long-term projects

Water supply & drainage: Municipal pipelines, buried water supply networks
Fire fighting system: Sprinkler and fire hydrant pipelines
Outdoor structures: Guardrails, street light poles, farm irrigation pipes
Industrial pipelines: Oil and gas transmission, chemical low-pressure piping
Overseas engineering: Infrastructure construction in Middle East and Africa

GP Pipe: Indoor use, low pressure, light structure and decoration

Indoor piping: Electrical conduit, air conditioning pipeline, indoor water pipes
Lightweight framework: Storage shelves, greenhouse frames, furniture structures
Temporary construction: Scaffolding, temporary fences, prefabricated houses
Mechanical accessories: Vehicle frames and light support parts

Usage Taboos

GP pipes are not applicable for buried installation, long-term outdoor exposure, high-pressure water delivery and fire protection system.

GI pipes are not recommended for interior decoration and ultra-light structural projects due to rough surface and high cost.

4. Common Misconceptions

All galvanized pipes never rust
Fact: GI pipe slows down rusting effectively. GP pipe gets corroded quickly in humid conditions for thin zinc coating.
GP pipe always brings better cost performance
Fact: GP is economical within 5-year service period. GI saves much maintenance expense for long-term service over 10 years.
Bright surface means superior quality
Fact: Bright GP pipe has poor anti-corrosion performance. Rough-surface GI pipe guarantees durable outdoor performance.