A new "green" exterior aircraft painting system in development by PPG's aerospace coatings business has shown corrosion resistance comparable to processes using chromated pretreatment and primers as well as easier application than for alternative environmentally responsible systems, according to the company.
The PPG Aerospace chromate-free depaint/repaint process includes a new exterior epoxy primer based on nanotechnology and an adhesion promoter PPG manufactures under license from Boeing, according to Alan Schoeder, PPG Aerospace commercial coatings global segment manager.
"In salt spray and filiform corrosion testing, metal surfaces protected by new Desoprime HS CA 7502 high-solids exterior epoxy primer showed the same corrosion resistance as those coated with chromated primers," Schoeder said. The PPG Aerospace environmentally-responsible primer is expected to be qualified this year at Boeing, he added.
Eldorado Adhesion Promoter (EAP-9) uses Boeing's Boegel technology that PPG has licensed, Schoeder said, enabling PPG to offer airframe manufacturers and third-party painters an easy-to-use, competitively-priced conversion coating.
"EAP-9 is applied to the stripped aluminum airframe and allowed to dry, and then Desoprime HS CA 7502 primer is applied," Schoeder said. "With a chromated process, the chemical has to be rinsed off, putting hazardous material into the rinse water. Unlike another chromate-free conversion coating, only one application is needed with EAP-9, and no mechanical abrading is required."
When EAP-9 is used with Eldorado corrosion remover and brightener EAC-8, resulting metal-corrosion resistance is similar to resistance achieved through processes using chromated chemicals, Schoeder said.