Brake drum FINALLY broke free last night. I used larger tip on torch and continued spraying with PB BLaster. When I again tapped edge of drum with hammer, I could see Blaster moving in and out of spline. That is when I knew that I was close. The rubber seal looks fine. I just have to clean up rust in cast housing. Brake drum will be sand blasted this weekend. Since no rain water could have gotten inside brake drum/casting area due to tight gasket seal, I believe rust was caused by condensation. But then again, wouldn't condensation form only on the exterior metal surfaces and not inside. Hmmm. Upon further thinking-- if tractor was run outside in cold winter weather, hydraulic fluid would get warm/hot. When parking tractor at end of day in unheated area, the housing cast metal would cool off at a much faster rate than the fluid. Since the hot fluid is on the other side of the casting wall, that would cause moisture condensation on the other side (Brake housing side). Does that sound right?? Thank to all for your valuable input. By the way, I will put either anti-seize or silicon on spline prior to attaching drum.
Do a search on "paraffin wax." Under the discussion of repairs and then "Wax used on rusted parts"