A method of manufacturing a granular perpendicular magnetic recording medium with improved corrosion resistance comprises sequential steps of providing a non-magnetic substrate including a surface; forming a soft magnetic underlayer (SUL) over the surface; post-deposition heating the SUL; forming an intermediate layer stack over the heated SUL; and forming at least one granular, magnetically hard perpendicular magnetic recording layer over the intermediate layer stack. Heating of the SUL prior to formation of the intermediate layer stack results in formation of an intermediate layer stack with a smoother surface and a granular perpendicular recording layer with increased corrosion resistance than when SUL post-deposition heating is not performed.