Chemical reaction between carbon fibers and aluminum :
Carbon fibers are commonly used to synthesize composites showing low density and high strength. However, carbon reacts with aluminum to generate a brittle and water-soluble Aluminum Carbide compound Al4C3
on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel
or titanium boride
No idea whether carbon fibers used by mast manufacturers are coated to prevent aluminum carbide formation at the interface between the aluminum collar (itself being passivated/coated against corrosion) and carbon fiber-reinforced ferrule...?
some sources of interest :