In-situ scanning tunneling microscopy (STM) and in-situ alternating gradient field magnetometry (AGFM) are used in combination to characterize the structure and magnetic behavior of Co/Au(111) layers electrodeposited from CoSO 4 solutions, with anions X=Cl - and SCN - added in amount traces. In the Cl - solution, the 2-D growth process is briefly recalled. In the thiocyanate (SCN - ) solution, preliminary observations show that nanometer clusters accumulate on top of a Co underpotential deposition (UPD) monolayer. Both structures solution/Co/Au(111) exhibit perpendicular magnetic anisotropy (PMA) for a Co thickness t=<t*, with t*~2 ML in the Cl - solution and ~4-5 ML in the SCN - one. Results are briefly discussed in light of classical models for PMA in ultrathin films.