Welding Finished Steel
Welding Finished Steel
(OP)
Hi all,
I'm currently working on a project that will have a trellis on the exterior. This trellis will be exposed steel HSS tubes. The trellis itself will be delivered in components and assembled in the field. The architect wishes to have all connections welded rather than bolted. Now, assuming that the steel will be finished in the shop, do I need to be concerned with the effects of the finishes (galvanizing, painting, etc.) on the field welding? Additionally, what is the best way to finish the steel to protect it against heat, moisture, etc. that it will always be exposed to?
Thanks
I'm currently working on a project that will have a trellis on the exterior. This trellis will be exposed steel HSS tubes. The trellis itself will be delivered in components and assembled in the field. The architect wishes to have all connections welded rather than bolted. Now, assuming that the steel will be finished in the shop, do I need to be concerned with the effects of the finishes (galvanizing, painting, etc.) on the field welding? Additionally, what is the best way to finish the steel to protect it against heat, moisture, etc. that it will always be exposed to?
Thanks






RE: Welding Finished Steel
You might consider weathering steel or stainless steel. Either can be welded and will perform well for exposed conditions. No finish is required on either.
If you use plain steel, prime the steel at the fab shop but tape off the weld areas so that you're not burning paint when welding. Then clean the welds, prime and paint the whole thing in the field.
RE: Welding Finished Steel
RE: Welding Finished Steel
Same with field welding the most common shop finish for outside iron and steel - the powder coating is destroyed by the grinding to clean the surface(s) and the immediate heat of the welding melts and burns the finish around the joint. Field "re-powder coating is impossible, and can (at best) merely be approximated by repainting the surface.
What does work for this kind of iron?
I've used a good primer painted very, very carefully into all parts of the joints (under, around, above, and in the cracks and crevices of the joints) and then followed by two coats of spray paint: each coat coming from a 45 degree angle from the horizontal from the four quarters of the small iron: left front down, left rear down, right rear down, right front down, (turn the piece over or spray up from below) and repeat: left front up, left rear up, right rear up, right front up.
Figure outside steel painted with a good primer (a galvanizing one is OK - just not as good a hot-dipped galvanizing process) wil last ten years. The cover paint to protect the primer from the sun and from the weather - and the primer is to protect the steel surface.
A bad paint job? 2-4 months.
RE: Welding Finished Steel
RE: Welding Finished Steel
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The finish of galvanized material when topcoated will not be as smooth as for other finishes, so that may be an issue for the architect.