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RE: Welding mild steel to stainless?

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Title: RE: Welding mild steel to stainless?

        Ralph,

                Richards webpage and Chris comments are both on the money. I have three items to add.

                A welder can make a good weld between galvanized carbon steel and Type 304 (304L, 316) without removing the coating first if the welder uses a whipping motion, moving the electrode around. This keeps the zinc out of the pool by melting or vaporizing it ahead of the pool.

                The next item is one that may not involve you. The welds I call out these days are structural and can be made with rods. But window frames are thin components and it is easy to blow-through when welding. The welder will probably want to MIG (possibly TIG) them because wire is much smaller than SMAW rods, so heat (thats the welders term, its really energy) is lower and blow-through is minimized. However, if any of the welding is done in the field, breezes will blow away the inert gases shielding the MIG arc, and SMAW is required.

                I do not know how long the galvanizing is expected to last, but it will be compromised beyond the stainless weld. If the intent is to delay rust as long as possible, that area should be cleaned as well as the steel was at the galvanizers and cold galvanizing or your other favorite coating applied. The steel of an uncleaned weld under zinc-rich paint outdoors often starts rusting within the first year, almost certainly within three years.

        HTH,

        Jim