In saltwater use it's a losing battle from day one. The last time I replaced my brakes I even bought a flush kit that mounts a fitting on each backing plate to spray inside the drum and has hoses that tee to a garden hose connection. Total waste of money and time. I doubt that added more than a couple of months to the life of the brakes.
The only solution I have ever seen that lasts was Kodiak SS disc brakes. They are by no means cheap and you still have to take good care of them. The Tie-Down brand discs have no where near the longevity of the Kodiaks.
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