Stainless-carbon galvanic reaction 3

[legner]

I have a project where I need to attach a stainless steel structure to a carbon steel structure. The stainless frame is mostly tubes, so bolting would not be practical. Does anyone have experience in attaching stainless to carbon by welding? Will this result in a galvanic reaction that will corrode the steel? AWS D1.6 prescribes how to weld stainless to carbon, but I do not want to interpret this as an endorsement of such a connection.<br>

 

[daski]

I have mixed the two steels on platforms in areas of biotech facilities, where the stainless steel is exposed to view and the c.s. is hidden behind walls or otherwise covered with gwb. e.g. welding s.s. guardrail to c.s. beams, etc.<br>
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What I have found out is: the two can be welded. I have not heard of any galvanic reaction. You should use an electrode that has more chromium in it than the base s.s., since it will be diluted by the c.s. Do this in order to maintain the anti-corrosive properties of the s.s. in the weldment.<br>
e.g., 309 electrode has 20% Cr, whereas type 316 or 304 s.s. has about 18% Cr.<br>
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s.s. has higher coef of thermal expn and will distort more readily from heat of welding. It also has lower thermal conductivity and will not dissipate heat as rapidly. Therefor, should use lower current, use skip welds and allow steel to cool between welds.<br>
Sparks from grinding will cause s.s. to rust.<br>
Call for fabricator to be asme chapter IX certified. Make sure welder is experienced with s.s. Someone who has only done c.s. welding will probably screw it up. Try to have this welding done in the shop, not the field.<br>
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Austenitic s.s. is most weldable.<br>
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I am not an expert is welding or in s.s., but have picked up these tips from a s.s. fabricator. Hope it is some help.

 

[MarkRPflow]

A good source for welding stainless steel is &quot;Welding Stainless Steels&quot; technical bulletin No. SS-300-C by Teledyne McKay, 850 Grantley Rd. POB 1509, York, PA 17405-1509 phone (717)-849-2490. Also the Nickel Development Institute (NiDI) phone: (416)-591-7999; <A HREF="

http://www.nidi.org"

TARGET="_new">

http://www.nidi.org</A>

 

[TJW]

I have worked in steel fab shops in the past, doing both structural and pressure vessel work. We routinely welded stainless steel to carbon steel, primarily using 304 and 316 stainless steel both straight and &quot;L&quot; grade. We used 309 filler metal which is fairly industry standard. We did not experience any galvanic type reactions, but if the stainless steel part is thin you can get carbon precipitation in the weld which can cause the stainless to rust in the area of the weld.<br>
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I hope any of this helps,<br>
<br>
TW

 

[legner]

We have decided to proceed with welding the stainless to the carbon steel. It does not seem to be a problem as long as the joint is not exposed to moisture. Thanks to all of your input.