I've been using a product called Purple Extreme on my firearms for a few years now, and have been very impressed with it. Product was originally developed for industrial use and now for commercial use. What impressed me was it's use on Aqua spin bike chains at our local Rec center. This is where you take a Spin bike from the Gym and place it in a pool and ride in the water. The chains never show any rust what so ever. Web site says it can be used on firearms and fishing gear. Check it out.
http://www.purpleextreme.com/