G.I. Pipe Welding

It may depend on the local regulations for preventing personnel exposure to toxic vapors. In former times, workers would drink lots of milk before welding on G.I., which alleviated nausea.

If you must weld on G.I., remove the zinc coating from the area adjacent to the weld. Afterward, the outside of the pipe can be painted with cold galvanizing compound, but there will still remain an uncoated area on the inside, which may corrode prematurely.

Only if:

• The galvanising inside the pipe is no longer needed for the purposes of corrosion protection from the fluids it is carrying and the contamination of the fluid with those corrosion products is acceptable (why not use ordinary carbon steel pipe instead? <rhetorical question - NNTR>, and
• The operative carrying out the welding is happy to suffer long-term health issues as a result of the zinc-rich fumes that are given off by such a stupid procedure and the firm that is ordering the work to be done is happy with the liability issues surrounding the authorisation of it.

This matter has been discussed in this forum before.

Don't weld galvanised pipe; screw it together instead.

Yes. Use MIG. Make sure to remove Zn coating from pipe by grinding and keep surface clean from grinding residues and oxidation.

If you must weld galvanized pipe, which you should plan not to do instead of having to do it, at a minimum the following equipment should be used:

1) a high velocity and sufficient volume dust/vapor removal ducted fan set as close to the piece being welded and the weld area.

2) a full face breathing air line supplied air face mask. Similar to a Self contained Breathing Apparatus (SCBA) but supplied from an air line connected to a breathing air pump or bottle cascade.

3) or instead of #2, a SCBA.

4) long leather sleeves that will be disposed of.

5) clothes that can be trashed.

6) hat or other head covering that will be trashed.

Yes, if it seems like you are encapsulating yourself you are. A full Level A or B haz mat suit would be appropriate but they burn from the splatter.

It is easier to strike and maintain an arc on galvanized than it is on uncoated steel.

Then coat the piece with several layers of cold galvanizing.

In order to avoid taking the risk that some body part, especially the respiratory system, is exposed don't do this. Engineer away from having to weld galvanized metals.

It can be done but requires a lot of equipment and caution if it is to be done correctly and with low risk.

Good Luck, Old Salt

Yes it CAN be welded.

Cautions have already been posted here so I won't repeat them.

If you are not legally obliged to follow any hazmat precautions then perform where there is good ventilation.

Why do you need to weld gal pipe? Are you building a fence, some other architectural accessory or fabricating/modifying a structural element?

If it's for plumbing then don't do it unless corrosion issues are not of interest.

First of all why you want to weld GI pipe when there are many fittings available for joining long pipe with coupling or angle bends etc. Better avoid welding.