The changes in environmental legislation in the early1990’s following the Montreal Agreement has resulted in the need for changes in the surface treatments used in the aerospace industry. This involves the removal of the CrVI ion from all processes and the use of low VOC (volatile organic content) or water based coatings. MaSSPS (or Materials System for Surface Protection and Sealing, a Brite-Euram project, BRPR CT-97-0538), incorporating 11 partners, aims to develop a fully integrated corrosion protection system using both of the above ideals. The system will consist of a Cr-free conversion coating, low VOC and water based, Cr-free primers, a Cr-free low density, fuel/water resistant, high adhesion sealant. The interaction of these new materials is complex and has to be understood in-order to avoid system failures in service. A key part of the airframe where these new materials will be used is the aircraft’s fuel tank. This is an integral part of the wing and, therefore, the coatings and sealants will be subjected to a wide range of temperatures, fuel and fuel/water mixtures and exposure to fungi that live at the fuel/water interface. This paper will discuss one of the many problems associated with a system of this kind. The challenge is to develop analytical methods to explore the surfaces and interfaces and understand their modes of failure. The surface analytical techniques used in the project are briefly described., which include XPS, ToF-SIMS, in-situ SEM tensile testing, AFM and µTA. The work will be described in a case by case basis rather than a discussion on individual surface analytical results.