The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Corrosion protection: fusion bonded epoxy vs. 3-layer system

What will provide better corrosion protection for steel plates 1/8" to 1/4" thick that will be welded in place: a single application of fusion bonded epoxy 12 to 16 mils dry film thickness or a 3-layer system consisting of zinc-rich epoxy covered with High-Build epoxy and a topcoat of polyurethane with a total dry film thickness of 10 to 14 mils? In both cases the surface preparation would be the same, blasted to near white metal. The FBE coating would be applied to individual plates in a shop specializing in this type of coating while the 3-layer coating would be applied after welding the plates in place. The application is as follows.

The locomotives on our railroad are experiencing serious corrosion (perforation) in steel plates in some areas. We are going to rebuild these locomotives in the near future and the corroded plates will need to be replaced. I would like to specify the maximum corrosion protection for the replacement plates without requiring exotic materials or processes. The corroded areas do not get any appreciable UV exposure but will be exposed to water, oil, Diesel fuel, some salt, and cleaning products. The cleaning products are compatible with polyurethane paint because this is our exterior finish and it is not affected by these products.

If we use the FBE coating, can a coat of polyurethane be sprayed directly on top of it or would an intermediate layer be required?

Ron Bartels
railroad - Montreal, Quebec, Canada
2004