Old 01-11-19, 11:02 PM
  #18  
repechage
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Originally Posted by machinist42 View Post
Filiform corrosion aka "filamentary corrosion" or "underfilm corrosion".

I politely beg to differ with the dire prognosis suggested previously, as I've generally found filiform corrosion to be readily checkable with an acid bath, I prefer phosphoric. though I suppose oxalic would work. In my experience filiform has been superficial. I'm not saying it can't erupt from within the tube, but I haven't seen that often. Mostly it's sweat spawned.
I agree here with the above, any rust can be a problem, but the speed of collapse if the coating is very variable.
The start is often at a thin film (as in paint film) condition that starts adjacent to a sharp turn of shape, lug point, cable guide, etc.
I agree that when addressed in a reasonable time it is of no big problem.
Every powdercoated frame I have bought has had this rust issue to correct. All of them.
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