To ensure the longevity of the commercial aircraft fleet, the long term durability of primary aircraft structure must be understood. The degradation of metals and their attachments (mechanical and adhesive) has been rigorously studied over the years. The introduction of composite materials in aerospace applications has presented challenges as methodologies that have successfully been used for metals do not always produce reliable results with new materials. This project will consider the effect of surface treatments on composite adherends and accelerated test methods that may be used to reliably compare their long term degradation. Follow-on projects will consider improving durability using nano-reinforced adhesives.