Yes there are preventatives, but it depends on exactly where the rust is. You prevent water entry to the frame by sealing the points of entry. Entry to a BB sealed bearing is more of a problem. On my old road bike which saw all weather riding, I cut 2 donuts out of foam, covered them in grease, and trapped them between the crank arms and bearings. These made very effective barriers to sprayed water, and I never had any bearing rust issues.
The other way is to keep bearings well greased with decent water resistant grease. Marine grade greases are great at this, but you have to keep the bearing greased. This is a problem with sealed cartridge bearings, most of which have no provision for relubrication. On some you can carefully remove the outer seal, grease the bearing and pop it back in place.
In any case, as I said, you had rusting too soon given the conditions, so depending on where and why, it might have been a case of inadequate lubrication from the factory.
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FB
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