Surely you would pick that up before a wheel fell off ?....?
Your use sounds like what all boat trailers in NZ do. Trailer axles here use a seal that doesn't seal on the axle, they seal on the hub, with a s/s sleeve. If used with a bearing buddy they will just burp a bit of grease and not blow out a conventional seal.
It went very fast. Heard noise roughly 100ft, was nearly at the launch, pulled in to investigate and the tough transition I think was the final straw.
As noted, this bearing was a year old.
A corroded bearing indicates seal failure. It doesn't take much to be a leaker. Power washing is another reason. Automotive wheel bearing seals withstand roughly 2 psi pressure. Those are sealed with 4 lips. I'm not that familiar with trailer bearings and their specific problems.
For sure it’s a seal failure. The seals on these spindles I’m seeing aren’t worth much. Here’s the other side removed this am. Difference is the outer bearing had a lot more (not very good) “grease” in it than the other side.
That said, I don’t think it’s power washing, unless the friction fit hub cap is to blame. We can’t easily pressure wash the back side of the spindle. That gets effectively 0 psi flush, briefly.
But these are third world launch points. The trailer is submerged, and often the rear of the truck is in the water...
Buy the real bearing buddies install them and follow the directions and never mind what you thought you know about greasing bearings because it isn't necessarily so You will need to buy and install shaft savers on the sealing surfaces on the axle so the seals will last and seal.
Im not so sure that “what I know” is so wrong, since the bearings in these Mercedes cars are often good well past 200k. I reused mine after my brake job, set properly, with the measured amount of grease. I’ve also seen firsthand when the grease isn’t measured.
What doesn’t happen with these is a bad rear seal.
There absolutely is a max amount of grease, for example, I found the SKF formula G = DB/10, where G is grease in ounces, D is bearing outer diameter, and B is bearing width.
There’s something also to be said about the amount of grease for a given speed of the bearing. These never see over 25mph. But I’m not aware of that calculation.
So for us, full overpack, given speed/distance might be ok, while it may have bad consequences if used, say, on highway.