GI pipe vs black steel pipe: which to use in Qatar
Both are welded steel tubes made in the same sizes. The difference is the zinc coating, and in Qatar's heat, humidity and salty coastal air, that coating matters.
What is the difference?
Black steel pipe (mild steel, MS) is bare steel with a dark mill finish. It is strong, easy to weld and the lowest-cost option, but it rusts if left unprotected.
Galvanised pipe (GI or pre-galvanised) is the same steel coated with zinc. The zinc protects the steel from rust, so the pipe lasts much longer outdoors with little or no painting.
| Black (MS) | Galvanised (GI) | |
|---|---|---|
| Rust protection | None until painted | Zinc coating from the factory |
| Welding | Easy, no special steps | Possible; grind zinc at the joint and touch up after |
| Painting | Needs primer and paint | Can be left bare or painted with a suitable primer |
| Cost | Lower | Higher |
| Best for | Indoor frames, parts that will be painted | Outdoor work, fences, shades, coastal sites |
When to choose galvanised
- Car park shades, canopies and pergolas
- Fence posts and gate frames
- Handrails and balustrades outside
- Anything near the sea or exposed to irrigation water
When black steel is fine
- Indoor frames, racks and furniture
- Structural parts that will be primed and painted anyway
- Heavy welding work where cost matters
Common sizes
Square hollow sections (SHS) commonly run from 20×20 to 100×100 mm, rectangular (RHS) from 40×20 to 150×100 mm and round pipes from ½" to 4", in wall thicknesses of about 1.2 to 4.0 mm and 6 m lengths. Thicker walls carry more load and resist dents.
Quick tip
If you weld galvanised pipe, work in a well-ventilated area, grind the zinc back at the joint first, and finish the weld with zinc-rich (cold galvanising) paint so the joint does not rust.
Need a price?
Call us or visit the store at Al Najma Souq. We'll check stock and give you a price on the spot.