If you dispense your beer with a party pump, which uses air instead of CO2 to drive the beer, you can only expect your beer to remain fresh for 8-12 hours. If you keep your kegs warm, and drive them with CO2 through a jockey box or other faucet, they will most likely last a couple of months.
Rust by definition is the result of the oxidation of metal. One engine manufacturer refers to the process of corrosion in aircraft engines as galvanic corrosion which is a type of corrosion caused by dissimilar metals being in close proximity of each other. In this process an electrolyte such as water also needs to be present. Almost all metals will oxidize or corrode.
Car Maintenance with 90+ answers. Most likely the same cause as would allow oil to leak into the car's coolant: A pathway between two fluid carrying systems (oil and coolant) in the car's engine has been formed, and now the two fluids are mixing when they ought not to be. Most likely cause would be a leaking - or blown - head gasket.