Bellypan/Undertray as rust preventative?

[M_a_t_t]

Would a bellypan help keep rust away from the underside of the car?

My thoughts are that if it was built of non-rusting materials (aluminum, ABS, etc.) it would keep dirt and water spray off of the car body. I can definitely see fasteners getting rusted and eventually broken upon removal, but that seems like a small price to pay to keep the rust away from the important parts.

[California98Civic]

I think that could work. You would want the belly pan to be pretty well sealed. Or at least you wouldn't want there to be big gaps that water could Splash through. I don't think you'd be able to prevent all rust since I'm sure it would get damp. And it would be humid. But you should be able to keep salt water from salted roads from getting directly onto most parts. But a downside would be that since frequent washing off of salty deposits during the winter is one of the methods for reducing rust, if any of the salt got through your undertray it would be difficult to really clean it really well without removing the undertray. I could see scenarios in which the undertray makes a rust situation worse.

[serialk11r]

A thought I had was instead of using fasteners (place where water can leak in), over parts of the body that don't need to be serviced (e.g. most of the floorpan aside from the center tunnel), you can attach a foam backed fiberglass panel with adhesives to the floor directly to basically make a smooth extension towards the ground.

The stuff they use to attach the hood support frames would probably work?

[cRiPpLe_rOoStEr]

Don't hold your breath for an underbody pan to work as rust protection. If it traps moisture or any corrosive residue, it's even worse as it may lead to a more difficult detection of initial signs of rust before the damage gets too bad. A good undercoating will fare better, even though it doesn't prevent the usage of an underbody pan for other reasons such as streamlining and protection against the impact of larger debris.