Let's start with cavity wax. Waxoyl, Fluid film, Eastwood's cavity wax are petroleum distillates that contain calcium sulfate. Originally it was used for plates on bridges to prevent corrosion between the two pieces of steel. It is also a lubricant has grease consistency it should be applied yearly. Por-15 was developed from the Mobay Bridge aluminum pigmented moisture cured primer. KBS coatings was a por-15 dealer who lost their distributorship when por-15 went nationally and they copied everything that por-15 did. If you want to seal your inner frame and hog troughs acid treat itmetal prep with zinc them follow it up 3 coats of the aluminum pigmented moisture cured urethane. To give you a comparison zinc phosphate epoxy primer three coats wIll do between 500 to 700 hours of salt fog. Mobay's primer 14000 and if it's scratched the rust doesn't travel beyond the chip. Invest in a Harbor Freight engine cleaning gun this little sprayer will blow paint and rust remover about 3 ft. great forgetting into all your hard-to-reach places.