Adsorption of N,N‘-Disalicylidene-1,2-propanediamine on 304 Stainless Steel

Abstract

The behavior of the jet fuel metal deactivator additive (MDA), N,N′-disalicylidene-1,2propanediamine in some high-temperature tests, has raised questions concerning whether it would decompose on contact with hot metal surfaces in aircraft engines and fuel systems. The adsorption of this additive was studied on oxidized and oxide-free 304SS surfaces using X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). XPS binding energy (BE) shifts indicated thermal decomposition on the surfaces. TPD revealed the growth of both physisorbed and chemisorbed states in accordance with the Stranski-Krastanov mechanism. MDA was only weakly chemisorbed onto the 304SS surface, with desorption energies of 47 kJ/mol on an oxidized surface and 33 kJ/mol on the oxide-free surface. These findings suggest that stainless steel would not likely contain a contiguous chemisorbed MDA multilayer that the adsorbed MDA could be removed from internal surfaces of aircraft fuel systems in regions of high-temperature and turbulent flow.