Plasma-sprayed aluminum and titanium adherends: III - Polymeric coatings - The effect of plasma-sprayed polymer coatings as primers on the durability of adhesively bonded aluminum and titanium

The durability of aluminum and titanium adherends, plasma-sprayed with polymeric coatings, and bonded with an epoxy and a polyimide adhesive has been investigated. Organic-polymeric coatings were plasma-sprayed using epoxy, polyester, polyimide, and cyanate ester components. Durability was investigated using a wedge-type specimen by exposing the specimens to an environmental cycle that included low temperature, high relative humidity at elevated temperature, high temperature at atmospheric pressure in air, high temperature in a vacuum, and room temperature. The systems exhibiting durability comparable with that for adherends treated using standard solution methods, included aluminum or titanium coated with a bis-maleimide/cyanate ester (B-CE) or a bis-maleimide-LaRC TPI-1500(R) (B-TPI) mixture and bonded with an epoxy or a polyimide adhesive. For these B-CE-and B-TPI-coated specimens, failure during exposure to the environmental cycle occurred in the adhesive, indicating a favorable adherend/plasma-sprayed coating interaction.