Powder Coating And welding 3

[NewbieStruct]

I am a new structural engineer.I am reviewing some comments on shop drawings. We have a steel beam to steel column welded connection. The architect has told me that he cannot do that since the beams are powder coated. So you cannot weld powder coated members?

 

[MikeHalloran]

I regard it as an opportunity lost for everyone.

The assembly certainly could be powder-coated and welded, but IMHO the architect failed in his responsibility to inform the structural guys that (s)he wanted to do something very unusual, OR the structural guys failed to read and understand whatever notice was provided, e.g. in an extra-thick specification.


( I.e.,
- The HAZ could be masked and not powdercoated, and hidden by a fascia or other construction detail.
- The completed welded assembly could be electrostatically powdercoated in situ, and baked in place by means of a temporary oven.
- The joints could have been specified as masked and bolted, with the bolts concealed, etc.

Painting to match the powdercoat is pretty much impossible. )


Mike Halloran
Pembroke Pines, FL, USA

 

[NewbieStruct]

I checked the original drawings, they had no mention of a powder coat. This was changed after the drawings were approved. Well, my boss is going to talk the architect about it. Thank you all.

 

[racookpe1978]

Beware of masking - Conventional (tape-based) masking methods won't work when faced with the high-temperature ovens and long baking times needed to melt the powder coating "granules" together into one continuous level surface.

 

[swall]

Mylar tapes with high temperature adhesive are available specifically for masking off powder coat and surviving the cure oven.

 

[gtaw]

If I remember correctly there is an OSHA requirement that paint and other coatings that can produce noxious fumes must be removed at least 4-inches from the area to be thermally cut or welded.

Such coatings would most definitely have to be removed from the area to be welded to prevent porosity in the welds and to minimize the introduction of hydrogen into the weld pool.

The welds and the surrounding area would have to be cleaned to ensure proper adhesion of paint to the steel or it would peel off in short order.

Bolted connections designed as snug tight would result in the least damage to the paint and overcome the problems associated with pretensioned bolted connections. Locknuts could be used if there is a concern with vibration and loosening of the snug tight bolts.

Some damage to the paint is inevitable, but the erector can take some precautions to minimize damage to the paint if he is made aware of the concerns before awarding the bid and providing a level of oversight on the job commensurate with the concern.


Best regards - Al

 

[racookpe1978]

Are these connections inside (exposed to the public's view) or outside (exposed to the weather) or hidden inside (behind a fascia or trim)?