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Corrosion resistance of TGIC polyester vs. epoxy
Q. I am looking for some opinions (and documentation if possible) on the differences resins play in corrosion resistance. As an example, assume all the same substrate, cold roll steel with an iron phosphate of 30-50 mg/ft2, DI rinsed and 1 mil of organic coating applied in the same method (i.e. wet spray, E-coat, powder). Which resin will do better for pure corrosion resistance - epoxy or acrylic.
I think I know the answer, but I am looking for a consensus of opinion.
- Mequon, Wisconsin
With sadness we note Dave's passing on Oct. 11, 2013. His longtime friend Anne Goyer offers a tribute to him in The Finishing Touch, Vol. 23 No. 4.
1996
A. I heard a presentation on filiform corrosion of clearcoats on automotive wheels at the Automotive Finishing show in Detroit this year, in which the presenters gave statistics which seemed to show that acrylics performed better than TGIC Polyesters. Epoxies were not considered for this outdoor use.
Andy BrushA. Just to add to Andy's response. We use epoxy and TGIC polyesters, and epoxies tend to give us better corrosion resistance than the polyester, however, we do not use the epoxies on outdoor applications since it will chalk in ultraviolet light, and discolor. We can pass 1000 hours salt spray with both with a 3 mil thickness. We do not coat any less than that.
Pete Smith- Nashville, Tennessee
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