Embodiments of the invention include a method for electro chemical mechanical polishing of a substrate. The process includes flowing an electro chemical mechanical polishing (ECMP) slurry having a high viscosity with a polishing agent over a portion of the substrate. Electrical current is passed through the slurry and substrate. The electrical current, in conjunction with the abrading action of the slurry as it flows over the surface of the substrate, serves to remove at least a portion of the metal layer from the substrate. The invention also includes various slurry embodiments.