What can I spray inside the trunk well to prevent rusting?

[atikovi]

I noticed under the spare tire some surface rust, some of it probably from the steel spare itself. I cleaned most of it off and want to put something there to reduce it from coming back. No paint, just something like an oil they used to spray under carriages with years ago. Can't be petroleum based as it would attack the spare tire rubber. Maybe silicone spray?

 

[matt_i]

fluid film it my friend!

 

[atikovi]

"FLUID FILM® is formulated from specially processed wool-wax, highly refined petroleum oils"

Don't think I can use that around rubber.

 

[matt_i]

Yes, youre right. In absence of painting you could goop it up with 100% silicone caulk and let it cure. Depending on whether moisture is migrating from an edge or thru porosity, it could work great or could be a bad idea and be bubbly rust underneath.

Or cut something like a plywood donut to insulate the tire edge from the fluid film.

 

[ItsNemo]

Why not paint? Spray on bed liner?

 

[rlitman]

Fluid Film will not attack rubber. But it’s odor isn’t a good idea in an enclosed vehicle. Undercarriage, sure, but not inside.

I’d suggest some paint meant to go over rust.

 

[atikovi]

I cleaned it up so just a few spots of rust on the surface. Will spray some silicone over it and call it a day.

 

[Robbie B]

I cleaned it up so just a few spots of rust on the surface. Will spray some silicone over it and call it a day.

All you’re doing is setting it up to rust worse. Unless you get all the rust off it will continue to rust under whatever you coat it with. Get a wire wheel and clean it all off then rattle can prime it and rattle can paint it. Doesn’t have to be expensive but it does need to be done right.


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[4xdog]

What's the root cause of water getting into the tire well? Until you address that, any other remediation is a band-aid that won't work long term.

Fluid film almost certainly won't attack the rubber on your tires. Just think about the implications if tires were attacked by other, lighter hydrocarbons? If a spill at a gas station led to tires dissolving? No, they've thought of this. The warning on Fluid Film is more likely for things like butyl rubber sealants, which aren't crosslinked like your tires.

But Fluid Film is messy. I wouldn't want it in my tire well. And silicone is a poor idea. It gets everywhere, interferes with adhesion of anything you'd like to stick to anything (like paint), and it's not going to protect from moisture. Don't go that route.

My recommendation would be (1) fix the source of the water getting in (or not getting out) and (2) paint the well with POR-15. It's kind of a pain to use, but it's simply *perfect* at things like this.

 

[ChrisLS8]

I cleaned it up so just a few spots of rust on the surface. Will spray some silicone over it and call it a day.

Do not do that. Silicone is a bad idea as is leaving some rust in there to spread again. You need to read up on some bodywork basics

 

[atikovi]

Well, you have grease and oil leaking down from the engine on to the frame of a 50 year old car and it's good as new.