Transition between metallic and non metallic surface?

For realistic results i should use constant 1 for metallic surfaces, and constant 0 for non-metallic surfaces. Problem is that texture mask which defines metallic have some filtering so there are some values between 0-1, that makes some bad results. Theres visible “outline” of metallic material as you can see on the picture. Is there any way to fix this? other than separate chrome parts with geometry.

Look into the node called AntialiasedTextureMask in the material editor.