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QUESTION:
Are "poison pads" on the exterior of stainless steel (SS) tanks still considered necessary for prevention of galvanic corrosion, or will the use of proper weld filler sufficiently eliminate the need for poison pads?
ANSWER:
What are poison pads?
ANSWER:
The term poison pads has been around a long time. It is a SS pad placed between a carbon steel (CS) vessel and a CS attachment.
A resident welding guru stated that these pads are for the prevention of CS contamination of the SS when welding a CS component directly to SS. We are, of course, referring to contamination of the inner surface (exposed to the process) by welding on the external surface.
He went on to offer (actually scoff) that in most instances this phobia was probably not founded in fact, but rather a knee jerk reaction to a possible problem. His point was that the carbon atoms would be able to migrate to the inner surface of the shell plate only if huge energy inputs (heat?) were involved. Since...