A general model for the hydrogen adsorption and hydrogen absorption into metals has been proposed. It includes reactions of hydrogen evolution M + H2O + e = MH(ads) + OH- MH(ads) + H2O + e = M + H-2 + OH- 2MH(ads) = 2M + H-2 hydrogen absorption MH(ads) = MH(abs) and hydrogen diffusion into metal. This problem leads to a system of differential equations which was solved using the differential algebraic equations method. Solutions were obtained for constant potential and constant current charging/discharging in the case of semi-infinite and finite length diffusion for planar, spherical, and cylindrical diffusion. Numerical solutions give new information about the reaction mehanism and may be useful in the determination for the kinetics of these processes.