FRP vs aluminum: corrosion, stiffness and fabrication

Aluminum's modulus is substantially higher than a typical pultruded GFRP profile. If envelope size is limited or deflection is strict, aluminum often reaches the target with a more compact section. FRP may still win when non-conductivity, thermal isolation or chemical resistance justifies a deeper section.

Do not compare density alone. A lower-density material can require more section depth to meet deflection, local buckling or connection limits. Compare the mass and cost of the qualified assembly, including joints and supports.

Aluminum performs well in many outdoor applications, but alloy, temper, finish, chloride exposure, alkaline contact and galvanic couples matter. FRP avoids metallic galvanic corrosion, yet the wrong resin can soften, crack or lose properties in a chemical/temperature combination.

If carbon fiber is present, electrically isolate it from aluminum unless the engineer has evaluated the galvanic couple. Fasteners, inserts and bonded plates should be included in the environmental review rather than treated as incidental hardware.

Provide the extrusion/profile drawing, support conditions, load cases, deflection, impact, temperature, fire requirement, electrical requirement, exposure, finish, tolerances, machining and annual volume. Ask for a marked-up compliance matrix and the source of every design value.