Summary for corrosion resistance resin Discussion
Corrosion resistance of TGIC polyester vs. epoxy is the core issue in this thread, but the excerpted question actually asks for opinions and documentation on how resin choice affects corrosion resistance on the same cold-rolled steel substrate with iron phosphate pretreatment, DI rinse, and a 1 mil organic coating. Dave Wright asks which resin would perform better for pure corrosion resistance, naming epoxy versus acrylic, and says he believes he knows the answer but wants a consensus. In the provided excerpt, no technical reply is shown, so there is no documented conclusion from the thread text itself. The page also notes Dave Wright’s passing and includes a tribute reference from Anne Goyer, but no corrosion-performance answer appears in the excerpt.
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.
Dave Wright [deceased]
– 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 Brush
A. 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