316 SS pipe welding to carbon steel

[CountOlaf]

I read over the thread realted to isolation flanges, but I figured it would be better to start a new thread...

Is it OK/common practice to weld 316L SS pipe to standard sch 40 carbon steel pipe or A36 steel plate? Are there any type of special welding materials/electrodes or special prep procedures that I should call out on the drawings/in specs?

Also, is there a dielectric issue with these dissimilar metals? I don't have water in the system. The application is more of a stack instrument test port nozzle.

And finally, if flanging/gasketing is employed, doesn't the gasket serve to dielectrically separate the two materials or do I need something else since the bolting bridges the materials?

Thanks in advance.

 

[MJCronin]

Olaf,

Suggest that you repost in a Welding forum

Yes, carbon steel can be welded to stainless. Tank fabricators do this virtually every day when the weld CS legs to SS tanks.

-MJC

 

[jay165]

Even if you had water, there isn't enough of a potential difference between CS & SS to worry about galvanic corrosion. 316L is preferred over 316 with 316L welding rods. It is commonly done as MJC suggests.

 

[CountOlaf]

Thanks guys for the responses.

FYI, I "re-posted" over at the "steel and stainless engineering" forum too. There did seem to be a little more interest/expertise over there.

 

[DavidMc]

CountOlaf,

Common practice for welding dissimliar metal like SST to Carbon would be to use filler material identified as 309. It come as a electrode for stick welding or slick wire for Heliarc. I'm a pipefitter by trade and I used it all the time for simple welds! All the way up to X-Ray joints. Hope this helped.

 

[stanweld]

CountOlaf,
Yes there is a major galvanic mismatch between 316 SS and carbon steel. Since your dissimilar joint is not in in contact with an electrolyte, you need not be concerned with the flanged joint needing electrical isolation. There are electrical isolation kits that can be provided for bolted flange joints.