Unless the installation is in a swamp or in an area of a high water table, I seal the ends of the main run where the cables enter and exit with puttylike removable duct seal.
If you must use sweep elbows and a riser, do not glue the couplings and leave the top enteies and exits of the conduit open to drain. Unlike line voltage conduits, they don't need to be sealed to provide protection.
Copper plated steel center conductor cable is just fine. The industry, other than satellite, went to it, because it is stronger and more durable when used in service drops and laterals and when pulled through conduits. Copper is only a factor, when it comes to long runs for satellite in runs near 200 feet. This is not for signal transmission, but for lnb switching voltage.
The ends are the key thing in preventing corrosion. Use good compression connectors. Place a dab dielectric grease on the tip of the center conductor before connecting.
The grounding blocks and all connections should ideally be placed in weatherproof boxes.
Following these recommendations, even non-direct burial cable will last for years and years, unless the cable's outer jacket is cut.