Well, this is one hell of a way to start on a forum.
Quick history:

-Girlfriend bought car in 2009 with 16k miles
-Car currently has 70k miles
-Purchased Hondas extended 100k/7yr warranty
-Zero issues with car besides a broken AC condenser from rock damage
-Installed an drop in AFE air filter
-Oil changes done by me every 5000-7000 miles, always with 5w-20 synthetic (usually Mobil1 or Wolfs Head, the latter actually gets better mileage and longevity via Blackstone reports)

I run a marina here in CT, and have an indoor heated shop that I work on my vehicles. The car has never been touched by anyone but myself since she bought it, besides my buddy across the street changing the condenser for me this summer.
I normally use Denso oil filters, once in a while I use Fram Tough Guard.
This last oil change I noticed a little bit of dampness on the bottom of the oil filter, with dirt clung to it, right where the filter meets the block.
No other visible leaks any where on engine.
Removed the oil filter to find a pitted section of the machined area where the oil filter seal resides.
It looks like galvanic corrosion (unlike metals eating away at each other).
I know the block is aluminum, the oil filters are steel- but they do no touch each other.

I tightened the filter a little more than usual this time to hope to stop the leaks. After a 10 min ride, it doesnt appear to be leaking.


This cant be the only time this has happened to someone.
Anyone seen this before?
I havent called Honda yet.
I dont really have a relationship with a dealership, because the car hasnt needed anything besides oil changes, front brakes, and tires.

Any ideas?
From my professional experience as a service manager and lead technician, this seems like it should be a short block replacement.

 

very strange. Sounds like a visit to your friendly Honda service dept. I don't see how corrosion is possible at the point you describe. Be interested to know what Honda says.

Too bad you didn't have a camera handy when the filter was off.

 

Is the most of corosion inside the seal ring surface or outside the seal ring surface?

If Inside ,it could be Hydraulic cavitation,but highly doubt it. Hydraulic cavitation is caused by extremely high pressures/heat and a foriegn liguid in the oil. It will actually blow chunks of metal away. Doubt the Fit oil system generates that much high pressure to cause cavitation. Happens a lot in high pressure hydraulic pumps and motors when the oil and say water mix and have very high temperatures and pressure internally.

Could be a salt water in the oil. If the block/tranny itself is all coroded white everywhere,I would say the salt environment,and possible salt concentration in the oil from either condensation from sea cold air or ingestion would be the cause. Given the area is normally protected by oil I would say salt water ingestion or exposure.

I drive an 2009 FIt and my block is still like the day I bought it ,bright,no dullness or whiting. However since my state uses salt on roads in winter the lower section of block,tranny are starting to dull from salt exposure. Corosion outside the seal ring surface would most likely from salt environment or exposure. I worked in a garage years ago and we could always tell a car from the ocean area by the whiting of engine blocks and trannys. VW dune buggies you could actually flake off engine block parts by rubbing them.

You mentioned having a marina,so I suspect salt exposure.

PaFitter