A kinetic study was performed for hydriding of TiFe and its alloy $TiFe_{0.8}Mn_{0.2}$ by pressure sweep method and another new method developed here. At initial stage the rate controlling step is chemisorption on metal surface and the rate equations of TiFe and $TiFe_{0.8}Mn_{0.2}$ at constant temperature, T and pressure, Po are expressed as
$F = 3.5\times10^{-2}exp(-800/RT)\frac{Po-Peq}{T^\frac{1}{2}}t$ for F<0.25
and
$F = 5.0\times10^{-2}exp(-1,000/RT)\frac{Po-Peq}{T^\frac{1}{2}}t$ for F<0.2 respectively.
At later stage the sorption rate is controlled by chemical reaction at the metal/hydride interface. The rate equations of $TiFe_{0.8}Mn_{0.2}$ are expressed as
$(1-F^*)^{\frac{1}{3}}-(1-F)^{\frac{1}{3}}$
=$5.6\times10^{-3} exp(-1,000/RT)(Po^{\frac{1}{2}}-Peq^{\frac{1}{2}})(t-t^*)$
for $F^*$ = 0.35, 0.35
