A protective sealing plug system for towing hitch receivers is provided having a main body for fittingly engaging within the cavity of a towing hitch receiver. The body is formed of a series of aligned segments each formed of a resilient or flexible material that retain oils or other corrosion inhibiting substances and hold them in place against the inside of the female receiver tube. A mechanism for urging the flexible material to compress slightly and, in the process, each segment expands slightly to allow engagement within the hitch receiver in a manner that both prevents access by outside elements, but also prevents egress of the main body from the hitch receiver until desired by the user. When installed in the female hitch receiver, the expansion of the resilient body will seal the female receiver tube and prevent the ingress of water, dirt or other damaging elements. Retraction of the resilient body will cause the flexible body to retract, allowing removal from the receiver hitch.