Mercury - Quicksilver Corrosion Guard Rust Inhibitor Spray 11 oz Can 802878Q55. Overview. Saltwater, moisture, and time - the three biggest enemies of metal on your boat. The Mercury Marine 802878Q55 Quicksilver Corrosion Guard is your first line of defense. This easy-to-use spray-on rust inhibitor creates a thin, water-resistant barrier that protects both painted and bare metal surfaces from corrosion and oxidation. Ideal for outdrives, lower units, power trim components, and exposed hardware,