Abstract: A grit blasting and alkaline etch surface pretreatment that is applied to a metallic airfoil. The metallic airfoil includes pockets or cavities that have been fabricated into the airfoil to reduce the weight of the airfoil. The pretreatment includes grit blasting the surface of the pockets or cavities, followed by washing the airfoil and treating the airfoil in an alkaline etch bath. After any remaining solution from the bath is neutralized and within twenty-four hours of the end of the pretreatment, primer is applied to the surface of the pockets or cavities. After the primer is applied to the surface of the pockets, a lightweight resin is injected into the pockets and bonds to the primer forming a mechanical bond with good fracture toughness at elevated temperatures.