Temperature-programmed desorption (TPD) of water from iron, chromium, nickel and 304L stainless steel

Water adsorbed at various temperatures in the range 373-873 K on chromium, iron, nickel and stainless-steel plates was studied by temperature-programm ed desorption (TPD) under vacuum (10(-6) hPa). Three states were distinguis hed: state I due to weakly chemisorbed water and states II and III probably associated with hydroxyl groups bound to different sites. Water is adsorbe d mainly in states I and II at temperatures T-0 < 500 K and in state III at T-0 > 600 K. These states were present in all the metals which were studie d except in iron that did not show state I, TPD spectra of water from stain less steel are explained by the presence of Cr and Fe in the form of oxides at the substrate surface. The heat of adsorption in state I and the activa tion energies of desorption in states II and III were found around 100-120, 170-190 and 220-270 kJ mol(-1), respectively. (C) 2000 Elsevier Science Lt d. All rights reserved.