Welding Galv. water pipe to Black Oxide Steel

[RikuY]

I have an application at work to weld hot-dipped galvanized water pipe to a black oxide, low-carbon steel chain sprocket. Currently, we are grinding the galvanizing and the black oxide finish of the sprockets to weld GMAW with Stargon. Is there another wire and/or gas combo where we wouldn't have to strip prior to the welds?
We cold galvanize after welding.

Thank in advance.

 

[metengr]

Rikuy;
If your current process works, I would not modify it to save a step in locally removing the zinc and black oxide in preparation for using GMAW (MIG). You can attempt to modify flow rates of the shielding gas and heat input, but I would not mess with it.

The zinc as it melts and vaporizes can wreak havoc with weld metal. Having a clean, properly prepared weld joint is the way to go.

 

[BillPSU]

I totally agree with metengr, for a sound weld you need clean base metals.
Do you need corrosion protection on the weldment? If so I would recommend hot dip galvanizing after welding and using "cleaned, lacquer removed" black pipe and the sprocket. This eliminates the grinding on the pipe and gives better corrosion protection. There are steel service centers which either stock bare pipe or can shot blast to remove lacquer coating.

 

[RikuY]

Thanks guys.
I figured that was what you were going to tell me, but I thought I would try anyway with this wonderful forum.


Thanks again!

RikuY