Corrosion on Flange Bolt
Corrosion on Flange Bolt
(OP)
Does corrosion will result in a carbon steel bolt
fastened to a mating flange of different material,
one flange is carbon steel and the other is stainless?
Please advise.
fastened to a mating flange of different material,
one flange is carbon steel and the other is stainless?
Please advise.





RE: Corrosion on Flange Bolt
RE: Corrosion on Flange Bolt
How about if I changed the bolt and nut material to alloy steel(e.g. A193-B7 and A194-2H), fastened to a carbon steel and stainless steel mating flange,
Is there any occurrence of corrosion on the bolt and nut?
Please reply.
RE: Corrosion on Flange Bolt
RE: Corrosion on Flange Bolt
As to methods to eliminate galvanic corrosion; electrical isolation is one method. Another is to find more "galvanically compatable" materials.
RE: Corrosion on Flange Bolt
For example, if that bolt is just exposed to the atmosphere, then that's not an electrolyte. So does that mean this type of corrosion is never a problem when only exposed to the atmosphere? That the objects have to be submerged or dampened for there to be a problem?
Are cast iron and steel dissimilar? Two different grades of carbon steel? Practically every bolted or riveted structural joint ever made has fasteners that are dissimilar to some extent from the base metal. Even weld metal is dissimilar from the base metal. Yet you really don't see this electrical isolation very often, nor do you see the corrosion that you might expect from the lack of it.
It's not too uncommon to attach carbon steel items with stainless bolts, although less common to go the other way.
We have customers who insist that galvanized items be electrically isolated from epoxy-coated carbon steel, and I have never quite understood the logic in that.
RE: Corrosion on Flange Bolt
As we have a pretty good atmospheric corrosion rate on CS at our site we use Teflon or Epoxy coated CS or alloy fasteners for flanges exposed to the atmosphere. We use uncoated fasteners, except a little copper based anti-seize, on insulated lines that are well above the dewpoint.
We have a tremendous number of CS/SS connections inside a building where both the temperature and humidity are high so we coat all Alloy fasteners with DAG, colloidal graphite. This is to assist in the removal of same.
RE: Corrosion on Flange Bolt
RE: Corrosion on Flange Bolt
good luck