The effective interface potential is derived for a superconducting layer attached
to a wall. The expression applies to the neighborhood of a continuous wetting
or delocalization transition, which exists for type I superconductors with a
negative extrapolation length. From this potential a number of features can be
easily derived, such as the locus of the phase transition and the critical
exponents. Whereas the order parameter exponent is universal, other exponents,
like the susceptibility exponent, are not.