Galvanised pipe vs black pipe — what's the difference?

Short answer: galvanised pipe for anything outdoor, wet, or exposed. Black pipe for indoor structural work, gas lines, or where you'll be welding it up and painting it over. Same shape, same wall thickness — what's different is the zinc coating, and that decides where each one belongs.

Black pipe — what it is

'Black pipe' is plain carbon steel pipe with no protective coating, just the dark mill finish on the outside. It's the workhorse of indoor structural work, gas piping and any job that's going to be welded, primed and painted. Cheaper per metre than galv. Welds clean because there's no zinc to burn off.

Galvanised pipe — what it is

Galvanised pipe is the same carbon steel, dipped in molten zinc after manufacture. The zinc coat is the bit that does the work — it shrugs off rain, salt air and the odd splash of pool water. Outdoor handrails, water lines, fence posts and bollards all want galv.

Side by side

When to pick black

• Indoor structural posts and bracing
• Gas piping (this is the standard)
• Anything you'll prime and paint anyway
• Hot-work jobs where you don't want zinc fumes in the welds

When to pick galvanised

• Outdoor handrails, balustrades and posts
• Fence posts, bollards, gate hardware
• Anything within a few kilometres of the beach
• Jobs you never want to maintain — set and forget

Welding galv — read this first

Galv pipe welds fine, but you have to grind back the zinc at the weld zone and ventilate — zinc oxide fumes from welding through galv are nasty. Once welded, hit the bare metal with a cold-gal spray to seal it back up. Same rule applies to any galvanised section.

Stuck between the two for your job? Ring the yard. We stock both finishes in the common sizes — we'll talk you through what fits the work.