Effect Galvanising on Welding Between SS and MS

Define MS flange. Specifically, what is the material?

Change the flange to stainless, or the pipe to mild steel then use the appropriate rod.

Yes the galvanising is a problem because at welding temperatures the zinc will for a vapour that migrates into the weld and causes embrittlement. Stailess steel cotains chromium and nickel these react with the zinc.

Sorry for the spelling errors I forgot to spell check, the answers given will give a good enough solution. Removing the zinc is the answer.

Dear BrainWave,

Never mind the spelling errors. Thanks for your comment. Can you please let me know the type of chemical reaction that takes place between Zn vapour, Cr and Ni?.The Grinding the weld metal is not helping as one of the respondent has indicated that even after grinding some traces of Zn is left behind to cause further cracks.Now I have decided to replace the galvanised MS sheet with the Un Galvanised sheet. Now my added problem is how do I give a corrosion protection to MS sheet as the component after welding will become rather impossible to go for hot dip galvanising. Is there any brushable coating that I can Give?

As Brainwave said.

Solution grind off the galvanising round the weld run.

Grinding off the zinc will eliminate the copious white toxic zinc-oxide fumes.

Main crisis still remains. In the weldmetal pool.

Resultant weldmetal is neither Austenitic nor Martensitic nor Ferritic.

Is just a horrible concoction of brittle alloys.

Nobody can help!

Go back to basics.

Have all SS .

Or all MS+SS cladding to take care of local corrosion.

The galvanising is mixing with the stainless steel rod being welded. You must grind off the galvanising, removing all traces at the weld joint to expose clean mild steel. Weld with a 308 grade or 316 grade Stainless steel electrode in 3.2mm guage and you won't have any further cracking problems. A slight pre heating of the joint to be welded when welding thick material above 12mm will also help.

Hello, Grind off the weld joint to clean MS and weld with only a E-309 rod. these rods are made for by-metal welding and are routinly used for MS to Stainless welds. They have a little more carbon as well as other materials in them to make the transition from SS to MS more agreeable and not brittle. I have a procedure for this type of welding and have proven it many times through destructive and non destructive testing.

Thanks, Pipewelder

You are correct'a'mundo

AWS CWI

Grind away any zinc in the affected weld area. Use rods for "Dissimilar Metals" and coat the area of the weld and affected zinc ( after it is welded and cleaned) with the material made by Belzona to coat the inside of pumps. Actually do this anywhere there can be galvanic reactions and stainless steel welds.