  We analyze theoretically the electrostatic interaction of surface-charged
colloids at water interfaces with special attention to the experimentally
relevant case of large charge densities on the colloid-water interface. Whereas
linear theory predicts an effective dipole potential the strength of which is
proportional to the square of the product of charge density and screening
length, nonlinear charge renormalization effects change this dependence to a
weakly logarithmic one. These results appear to be particularly relevant for
structure formation at air-water interfaces with arbitrarily shaped colloids.
