  The effect of diffusion on the chemical composition of subdwarf B (sdB) stars
and of hot white dwarfs strongly depends on the presence of weak winds. In the
paper, for stars with half a solar mass, for various effective temperatures
between 25000 K and 50000 K, and for various metallicities between solar and
1/100 solar, the mass loss rates are predicted as a function of the surface
gravity. With assumptions similar to the original theory of radiatively driven
winds, the method of solution of the momentum equation has been modified,
because the usual parametrization of the line force multiplier leads to
complications in the case of weak winds. According to the results, weak winds
with mass-loss rates of the order E-11 solar masses per year may exist only for
the most luminous sdB stars. For the more compact ones, the decoupling of the
metals from the bulk matter (hydrogen and helium) is expected in the wind
region, because the momentum exchange via Coulomb collisions is not effective
enough. Thus multicomponent effects are of great importance. For the case of
white dwarfs no wind solution exists at all, if multicomponent effects are
neglected.
