RTV silicone rubber compositions are provided comprising (A) an organopolysiloxane, (B) an organosilicon compound or partial hydrolytic condensate thereof, and (C) a non-aromatic amino-bearing compound. The compositions, when electric and electronic parts having a copper, silver or other metal portion on their surface are encapsulated or sealed therewith, can prevent or retard the parts from corrosion with sulfur-containing gas.