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I have my outback stored in an enclosed garage in DE during the summer. It's about to come out of its 3rd summer of storage, and spending time under it looking at the underbody I notice that surface rust on some but not all of the large steel components of the undercarriage (suspension arms, mounts, brackets, drivetrain parts) has increased over the summer. I also find white powder deposition on some parts that look like they're aluminum (transmission housing, can't remember what the part was but remember it had that dull gray look of aluminum).

This is disturbing because I don't want my darling rusting continually while I think that I'm giving it good care by storing it in a nice garage.

I think what's happening is:
- the garage is on the ground floor of the building, a poured pad
- in the summer, the garage gets quite warm (it's heated but not cooled)
- the air is humid all the time, with marine humidity because it's about 200 yards from a salt marsh and bay
- the car is on 3/4" boards (on tires) on a plastic sheet over the concrete floor
- I suspect that the relatively cool floor is creating a temperature gradient compared with the rest of the warm summer air in the garage, the metal undercarriage in this cooler environment gets condensation of the moist air in the garage, and particularly because it's marine air, rust and other surface corrosion form

solutions I've thought of, fall into two categories:

a coating for the underparts of the car.

- I see the body panels are already undercoated, I'm thinking of something to spray or brush onto the suspension members, drivetrain components and brackets, etc. that would seal the metal surface against the moist air.
-- I'd prefer not to have to do extensive surface prep first. Thus, something that converts the rust or at least stops it from expanding its activity would be preferred
-- if I can do it myself I will, otherwise I'm interested in commercial solutions where I pay someone to do it
-- if it needs to be reapplied each year because of abrasion, washoff etc. that's not a showstopper

a coating for the floor:

- I don't really think this will solve it because of my suspicion that the temperature gradient is the primary actor and the car is on a plastic sheet so that moisture transfer through the floor to the region of the car underbody shouldn't be significant. But if you disagree or have experience with a good solution, I'd like to hear about it

Solutions which aren't viable are to run A/C to the garage, or to run a dehumidifier in the garage. Weatherstripping the garage to decrease humidity is a low-likelihood maybe (because I suspect it won't work well enough to be worth it - again, if you disagree, glad to hear it.)

Thanks for any ideas...
 

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"the air is humid all the time, with marine humidity because it's about 200 yards from a salt marsh and bay"

You can't change the climate.
Sounds like you are seeing surface corrosion on unpainted or unprotected hard parts under the car. That's normal and harmless. If Subaru felt the part needed corrosion protection it would have been added at the factory.

If you are concerned, spray some WD-40 liberally on the parts next summer.
 

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You might consider a sacrificial anode. If the air in the garage is not circulating much, I could see it helping you.
 

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...I can't see it being the maritime air. I live in Newfoundland...that's as maritime as it gets...and the eastern most point of North America. I don't have any rust issue on our OB as of yet.
 

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Your fighting a perfect storm, and may not win. Locationlocationlocation, all bad in this case.

Marine air can be very corrosive. A humidifier would be best. An enclosed garage in summer in salt air is just as bad as a heated garage in winter in the snow belt.

Would a fan be possible?

Why is the car stored like this?

The white powder on the aluminum is harmless, ugly but harmless. It is just the aluminum oxidizing. All uncoated aluminum will do it with time.
 

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Discussion Starter #6
thanks all - Scooby from Newfoundland, I think the difference may be that it's warm in the summer in DE (not making jokes at Newfoundland's expense - but how warm does it ever get in an enclosed garage in the summer at/near your home?)

Rasterman - I've heard of sacrificial anodes used on boats to prevent electrolytic effects. Where/how would I apply one in my environment ?

Nipper - I'm assuming you mean a de-humidifier ?
 

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thanks all - Scooby from Newfoundland, I think the difference may be that it's warm in the summer in DE (not making jokes at Newfoundland's expense - but how warm does it ever get in an enclosed garage in the summer at/near your home?)

Rasterman - I've heard of sacrificial anodes used on boats to prevent electrolytic effects. Where/how would I apply one in my environment ?

Nipper - I'm assuming you mean a de-humidifier ?
Being a boat owner and knowing how the Anode works - either someone failed HS science or they have discovered some new type of science where Anodes work on cars not sitting in water at a dock.

My 2001 Legacy was parked for 10yrs outside where ocean salt blown off the Pacific Ocean would cover the windshield overnight. Even with a dent in the door where the paint had been creased and bare metal was exposed rust was nearly a non issue. At 140K I replaced a two wheel bearings one was rough the other one was probably OK - all the under carriage parts were rust free and easily worked on. A same generation subaru from Michigan where they salt the roads would be an utter and complete rust bucket compared to my car.

Parked in a garage - your tools rust while in the tool box? I know mine did! If your really worried about the car or your garage stuff - air flow ie venting or if you want to get crazy like what we do on the racing boat to keep it dry and light - we have a dehumidfier set up to dry out the air etc.

By the way Zinc's on boats for those of you who don't know are there to spin off electrons given boats are not grounded and most boats have various electrical items on board. The zinc as it spins off electrons sheds its mass and eventually needs to be replaced. A boat with metal parts in the water like props - drive shaft supports etc that does not have a zinc will shed electrons from these harder more costly and important metal objects. If ignored your prop - drive shaft and other critical components will become like swiss cheese and break. In the case of drive units that fit through the hull like sail drives a rotten sail drive unit could fail and sink your boat due to the large hole it just created when it failed.

Sail drive units early on suffered major issues from this due to the small zincs and people not changing them and also zincs which were not making metal to metal contact. A zinc that is insulated from the metal it should be protecting either by paint or some other type of coating is no longer the piece that bleeds off mass the engine or critical boat part is the item that spins off its mass.

The other issues which zincs do not address are opposing metals reacting to each other in a salty marine condition which case the metals are simply eating each other up nothing you can do but either isolate them from each other or use different metals.
 

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I've seen anodes installed in the belly bays of specialty trucks- mobile MRI scanners, outside broadcast tv trucks etc. Possibly they are just wasting their money, but the operators seemed to think they helped.
 

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I've seen anodes installed in the belly bays of specialty trucks- mobile MRI scanners, outside broadcast tv trucks etc. Possibly they are just wasting their money, but the operators seemed to think they helped.
This is not done for the purpose of rust prevention.

These trucks are rolling high voltage vehicles with a whole lot of odd ball things going on. And no it has nothing to do with rust.
 

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MO I mean a fan. Get the air moving through the garage and not trapped in the summer heat. It will help reduce the rusting somewhat, if not greatly.
 

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MO I mean a fan. Get the air moving through the garage and not trapped in the summer heat. It will help reduce the rusting somewhat, if not greatly.
^ might also address any structural issues your garage might suffer from moisture build up from improper venting etc.
 
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