A rotor blade assembly for a wind turbine includes at least one rotor blade having surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a blade tip and a blade root. The surfaces are constructed of a polymeric composite material. The rotor blade assembly also includes a protection cap arranged adjacent to one or more of the surfaces of the rotor blade so as to cover at least a portion of the one or more surfaces of the rotor blade. The protection cap includes a body defining an overall length. Further, at least a first segment of the protection cap is constructed of a tungsten-based metal. Thus, the protection cap is configured to reduce erosion and resist corrosion of the rotor blade caused by particle or liquid impact.