Thermal stressing of Jet-A was conducted in a flow reactor on iron- and nickel-based metal surfaces at a fuel flow rate of 1 mL/min for 5 h at a wall temperature of 350 degrees C and 3.5 MPa (500 psig) so that both liquid-phase autoxidation and thermal decomposition of autoxidation products contribute to the formation of carbonaceous deposits. The deposits produced were characterized by field emission scanning electron microscopy (FESEM) and temperature programmed oxidation (TPO). The effect of metal Surface on deposit formation increases in the following order: AISI316 < AISI 321 approximate to AISI 304 < Inconel 600 < AISI 347 < Inconel 718 < FecrAlloy < Inconel-750X. The variation in the activity of the metal substrates is attributed to their reaction with reactive sulfur compounds in the fuel and interaction of oxygenated intermediates formed by autoxidation during thermal stressing.