Design Philosophy for Corrosion Protection of Civil Aircraft

A new corrosion protection system developed at B.A.C. Weybridge was first introduced on Vanguard aircraft and has remained in use almost unchanged up to the VC10 and B.A.C.1 11 aircraft which are being produced at this time. The system represented a complete change from previous ones, both in materials and methods of application and was the result of a very considerable amount of research into the limitations of the protective methods used up to that time. Through these investigations it became evident that insufficient emphasis had been placed on the importance of organic materials in corrosion protection and that the paints then in use failed to give satisfactory service due to lack of adequate‐fluid resistance and an inability to withstand repeated flexing and straining of the metal substrate without cracking of flaking. Hence the paint had to be resistant to all anticipated contaminants, including freight spillage, over the entire temperature envelope of the aircraft and had to be sufficiently adherent and flexible to withstand deformation of the substrate up to the point of metal failure. Long term protection from corrosion and compatibility with other forms of protection e.g. sealants, jointing compounds, etc. was also required, as well as an ability to withstand casual damage during service and maintenance. This lead to the decision (hat the Vanguard was to be an all‐painted aircraft and that the many and often conflicting requirements of the paint could only be met by a polyamide‐cured epoxy material. Having thus established the basic concept, consideration can now be given to the detailed requirements.