Welding Problem

You may weld. I've seen some guys do that with ordinary GTAW (just use low carbon consumables as a safe direction). Some report that an austenitic low carbon rod also works fine. Just keep in mind that, in a marine environment, you're prone to galvanic corrosion, and the weld should be done really carefully to avoid sensitization of the stainless steel side. Do you really need to join two dissimilar materials with weld in such aggressive media? Could you go for all stainless steel or, even better, do a good job with mild steel and give it a good painting for protection? Think about it...

I have welded MS to SS using flux cored MS welding wire for outdoor NON-CRITICAL applications with great success. I'd suggest MIG/TIG/Argon w/1%O₂, and using SS wire, 309 I guess.

SS wire brush clean. Take care not to transfer any MS particles to the SS side as this WILL cause rust.

Prime and paint with marine grade epoxy.

Good Luck.

I think SS wire with either MIG or TIG would be fine however you will want to passify the result with Nitric Acid scrub whe complete. I'd ensure you have a Zinc Anode in good contact with the MS side as well.

Hi Buck

I used to make large steel boat rudders with a bottom section that pivoted, I would turn about 1/8" off the MS shaft and replace that with 316 weld. This was done before the shaft was welded to the rudder, I then re-machine the shaft to size. The entire rudder would be hot dip galvanised and when the bearing journal zinc wore through in service, the stainless would stop the corrosion. Worked well.

Hi Buck!

The answers you have received so far are nonsense and are not from professionals. Use 312 or 316 Stainless with Arc, Tig or Mig depending on the thickness, application and what technology you have. Using anything else specialised would be overkill. Using mild steel etc will cause ferretic weaknesses in the heat affected zone. Cheers!

Micko

I am so glad we have a professional on board, we all stop answering now. I might point out the rudders I am referring too, are still fine after 30 years. Maybe you should keep your arrogance in check if you wish to contribute.

I apologise if I sounded arrogant! Your answer was not even on the site when I sent mine through!? You must be a very insecure person. Sorry.

PS There are, of course, a lot of ways to skin a rabbit as there are ways to weld. Metallurgy is a science and scientists are accustomed to others disagreeing with them. It's up to the individual to decide which doctor they see and listen to and it may depend on how much the Dr costs, what equipment they have, where they are, what the medications cost etc etc!! Buck is the decision maker.

Buck is the decision maker.

Unfortunately you are correct Micko..............I also think that many seek out the cheapest Doctor, who should have been struck off years ago.

.....where they are,......

....and I wonder where they are? I had better not answer that, I have already been accused of being a bigoted racist in another forum for sticking up for someone, whom I thought asked a perfectly sensible and legitimate question.

^{I hate confrontation}

Talking of insecurity Micko, I note you don't provide any information about yourself.

My comments were referring to your rudeness to all the contributors, not just me.

Must be a very, very small shaft on your motor!!

By the way. your answer is almost the same as mine!!!!???

To be your first post, that's not a good entry; for now on everybody will oversee your technical proficiency and only remember your pedantry.

Too bad, I'm sorry for you, my advice: Create a new user account and log-on as such, pretend this never happened and don't sign as Micko! again.

U must be a welding rep!!

Thank you for enlightening all us non professionals on the only way to join two dissimilar metals.

It probably won't do any good to suggest that your way may not really be the only way to join these materials. There are those of us out here who, in our ignorance, have been doing it wrong all these years and, apparently have been lucky.

Thanks for your learned, modest response.

You know how to make an entrance, for sure.

I agree!?

312 is a good consumable for welding SS to MS.

Clean and dry surface is a must, hence good cleaning by wire brush is usefull.

You will have to consider section thicknesses etc for setting the welding parameters.

Hello Buck

We regularly weld SS to MS using Betanox-D, Chem (c-0.08, Mn-1.6,Si-0.6,Cr-23.5, Ni-13.0)

Stainless steel? What 304, 316, 321, 347.........? series 400?.........Ferritic SS?.....

Wherever , may be you can buttering the MDS side with 309 and weld both with 308. You need to prepare a WPS/PQR.

For marine enviroment, organic zinc is a good primer, and there are a lot of differents intermediate and final paints. Ask your paint supplier.

WHAT! Sir!!

Welding mild steel to 316 stainless (I assume). The SS may be okay, because the mild steel will act as a sacrificial anode, and prevent galvanic action. meaning of course, the plain carbon steel (mild steel), will corrode.

A good cathodic protection system may be an advantage, however biofilm corrosion can occur in SS's and may cause extreme acid environments with pH values less than 2, which of course causes rapid, corrosion problems. This can even occur in Super Duplex SS's as well.

You may find some interesting reading at www.corrodim.nl and of course many other sites that deal specifically with marine and off-shore corrosion.

I am very interested in this topic, but your link bombed when I tried it.

My sincerest apologies..........I wasn't watching my spelling.

Here goes, I'll try again.........www.corrodium.nl..........Hopefully this one will work for you.

An industry standard is to stick weld it with 7018 rods. As for the cleaning, I'm not sure.

The most common joining material for welding Stainless to Mild steel is some form of 309 or 309L. Since Carbon steel is a part of the weldment, the heat affected zone will contain some Chromium Carbides. The interpass temperature may be kept below 350 F to help reduce embrittlement. The Cr C cannot be eliminated but if there is burning slag, clean it by grinding to clean surfaces. If the stainless has been cut with Plasma, that area must be ground back about 1/16".

As an alternative, Monel welding material may be used. Monel is probably the most widely used material to prevent erosion and corrosion in most marine applications. This is a more expensive approach and may not produce enough advantage to merit the cost.