The variation of the stoichiometric composition of amorphous hydrogenated carbon films (a-C:H) deposited onto stainless steel was determined as a function of various elaboration parameters (pressure in the reactor, generator power, gas flow rate), by energetic alpha particle scattering (elastic recoil detection, nuclear backscattering spectrometry). Whatever the experimental conditions, the films obtained present the following characteristics : a hydrogen-depleted surface layer (approximately 40 nm thick); a deep-lying layer of constant stoichiometry and of variable thickness according to the elaboration parameters. Furthermore, strong hydrogen diffusion inside the substrate is observed. The total hydrogen content decreases when the pressure in the reactor or the generator power increases and it goes through a maximal value when the gas flow rate increases. In the limited range of total hydrogen content studied here, no significant variation of the adhesion properties was found.