In one embodiment, a method for activating a metal layer prior to depositing a cobalt-containing capping layer is provided which includes exposing the metal layer to an electroless activation solution to deposit a palladium layer on the metal layer and depositing the cobalt-containing capping layer on the palladium layer. The electroless activation solution contains palladium nitrate at a concentration in a range from about 0.01 mM to about 1.0 mM, nitric acid at a concentration in a range from about 0.01 mM to about 3.0 mM and water. In another embodiment, the electroless activation solution contains palladium nitrate at a concentration in a range from about 0.01 mM to about 1.0 mM, methanesulfonic acid at a concentration in a range from about 0.01 mM to about 3.0 mM and water.