Mating Carbon Steel Pipe Flanges to Stainless Steel Pipe Flanges 2

[RiniEIT]

I have a 3" pipe spool with a carbon steel WN RF CL150 flange (ASTM A105) and it needs to be bolted to a mating CL150 flange made of stainless steel (ASTM A182).

Are there any practices that I should be aware of, to prevent galvanic corrosion, when bolting the two dissimilar flanges together?

Thanks.

 

[pennpiper]

RiniEIT,
First of all the two flange faces do not and will not touch.
You would only need to consider the CS nut touching the back face of the SS flange and the CS bolt coming in contact with the ID of the SS Bolt Holes.
This is normally taking care of by using nonmetallic Insulating Gasket Sets (go here for example:

http://www.apsonline.com/gasketkits

)

Sometimes its possible to do all the right things and still get bad results

 

[rconner]

In the absence of electrical isolating means, and if the connection is exposed to or submerged in an electrolyte, there would likely be some corrosion of less noble material (i.e. carbon steel) in this coupling. If you were to provide more information concerning your application to know if such conditions exist, or would be detrimental to the service, those with more direct experience could probably provide better information.

 

[RiniEIT]

Thanks guys. Yes sorry, I do realize that a spiral wound gasket is typically installed between flanges and as far as galvanic corrosion issues, it would be the carbon steel hardware touching the stainless that I was concerned about. Thanks for the link for the isolating hardware kits. The isolating sleeve w/ washer is exactly what I'm looking for.

 

[LittleInch]

If you have a look or search in the corrosion engineering forum in material engineering there are many posts like this.

Key is what is the relative mass between the two different materials and where does the electrolyte come from. Massive amount of C Steel and a single Stl Stl flange - not much issue. Think of how many instrument connections you see and there are no insulating gaskets. Other way around - big issue

Be careful about internal corrosion with conductive fluids.

Isolating sleeves and washers with bolts are notorious for breaking down over time or being damaged during installation. You sometimes need thinner bolts as well which causes all sorts of grief.

But work out whether you have an electrolyte or not first.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JezFullham]

The flow is important here. Is the medium (Water, Oil, Gas etc.) flowing from the Carbon steel flange into the stainless steel flange, or vice versa? From a material stand point, if the water flows from stainless steel flange into the carbon steel flange, the corrosion will occur quicker with the carbon steel than usual. if the flow is the other way, carbon steel to stainless steel, it should be a very big issue.

In general it is always recommended to have same materials installed when it comes to flanges and pipes. Furthermore, in the field I am in, stainless steel flanges are a must and the only thing that will really last.

 

[moltenmetal]

So boring to see the same questions posted again and again...

You didn't post the service (the fluid flowing in the pipe), or the external corrosive environment, whether or not the pipe is insulated and/or heat traced etc., so we can't advise you at all whether your best option is a) do nothing special, other than perhaps painting the carbon steel pipe and flange, or b) use a flange isolating kit and a NONCONDUCTIVE gasket, i.e. NOT a spiral wound gasket!.