Using electrochemical scanning tunnelling microscopy, we measured the potential-dependent kink energy and the corresponding dipole moments for kinks at step edges on vicinal Au(001) surfaces in chloride and bromide containing electrolyte. Combining the results for the potential dependence of the kink energy with impedance spectroscopy data for the surface charge, we can directly deduce the dipole moment of kinks at the Au steps with co-adsorbed Cl-, respectively Br-. We find μ^Cl= (6.0±0.7) × 10^(-3) eÅ and μ^Br= (10.1±0.6) × 10^(-3) eÅ.