  When we place conducting bodies in electrolyte solutions, their surface
potential $\Phi_s$ appears to be much smaller in magnitude than the intrinsic
one $\Phi_0$ and normally does not obey the classical electrostatic boundary
condition of a constant surface potential expected for conductors. In this
paper, we demonstrate that an explanation of these observations can be obtained
by postulating that diffuse ions condense at the "wall" due to a reduced
permittivity of a solvent.
  For small values of $\Phi_0$ the surface potential responds linearly. On
increasing $\Phi_0$ further $\Phi_s$ augments nonlinearly and then saturates to
a constant value. Analytical approximations for $\Phi_s$ derived for these
three distinct modes show that it always adjusts to salt concentration, which
is equivalent to a violation of the constant potential condition. The latter
would be appropriate for highly dilute solutions, but only if $\Phi_0$ is
small. Surprisingly, when the plateau with high $\Phi_s$ is reached, the
conductor surface switches to a constant charge density condition normally
expected for insulators. Our results are directly relevant for conducting
electrodes, mercury drops, colloidal metallic particles and more.
