Welding with a little bit of paint after grinding 5

[lsmfse]

We have an existing beam to column connection that we now have to weld the shear plate to the beam web.
The existing connection has been painted.
The welders can grind most of the paint away, but cant grind all the paint at the joint.
Please, all the CWI's respond, anyone else with experience, any suggestions?

 

[dhengr]

lsmfse:
After grinding and other prep., burn the remaining paint off with a torch, clean up the ash with a powered wire brush and a hand brush, then wipe the surface down. There are some fluxes and rod coverings which are somewhat tolerant of slight surface impurities. I don’t intend to mean you can weld through a puddle of paint, oil or water, but you don’t need a shot blasted clean surface either. Talk with a few local welding material suppliers for their weld prep. recommendations.

 

[DVWE]

Agree with dhengr.

The devil is in the details; she also wears prada.

 

Sounds like a plan.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[racookpe1978]

In practice, GTAW will almost always fail (porosity, inclusions, surface defects) if anything but a very clean newly-ground surface is welded.
SMAW is more forgiving to very small bits of paint left on the surface - if, for example, paint is removed by simple hand wire brushing or impact hammer (needle gun). Your best weld requires the weld to be melting together clean filler, clean base metal, and new clean metal.

 

[gtaw]

While the SMAW or even FCAW will tolerate a little residual paint and still produce a respectable weld, I find it interesting few people consider the age of the paint to be a concern. If the structure was built before the 1980's, I would question whether the paint was lead based. Grind, burning, or welding is going to "release" the lead into the worker's breathing area. Then again, some people consider their workers to be expendable. Can't say I agree with that approach. Get the paint tested if it has been in place for 30 years.

Best regards - Al

 

[Compositepro]

There are no welding fumes that are safe to breathe, so what are you going to do differently after you get test results?

 

[gtaw]

You can't protect the welder if you don't know what you're dealing with.

Best regards - Al

 

[DAVIDSTECKER]

Maybe use paint stripper and a wire brush once the paint has lifted.

 

[pre_engineer]

A good old stick/arc/SMAW welder will weld straight through the paint/rust easily. I'm glad at least some people know the health concerns...


you're going to need less than $100. The mask that will actually protect from lead and mold and any, ANY other unknown particles is called:

-3M 60926 Multi-Gas/P100 (HEPA)


The 3M 6000 series is the one you want, the p100 is a hepa filter is needed whenever you are using heat or vaporizing these bad chemicals, the 926 version has an extra charcoal filtering so they won't be inhaling vaporised lead.


This is a cheap mask... please do not make them wear a cotton mask that will only serve to capture particles and force the user to breathe all their air through a blackened cancerous cotton ball (been there done that found a new job).


Replacement filters are below $30 by the way. also they make a half face version so it's small and will fit under the welders hood. It must fit under the mask or the welder will complain and not use it