  It has been established for a long time that the long range van der Waals or
thermal Casimir interaction between two semi-infinite dielectrics separated by
a distance $H$ is screened by an intervening electrolyte. Here we show how this
interaction is modified when an electric field of strength $E$ is applied
parallel to the dielectric boundaries, leading to a non-equilibrium steady
state with a current. The presence of the field induces a long range thermal
repulsive interaction, scaling just like the thermal Casimir interaction
between dielectrics without the intervening electrolyte, {\em i.e.} as $1/H^3$.
At small $E$ the effect is of order $E^2$ while at large fields it saturates to
an $E$ independent value. We explain the results in terms of a decoupling
mechanism between the charge density fluctuations of cations and anions at
large applied fields.
