Rust

[Spellino]

Having bought my sedan 2007 a month ago, used, I just discovered this amount of rust under the driver seat. I will take it to the mechanics but I wanted your opinion on the possible fixes for this. Would it have to be welded?

[06YarisRS]

That's nasty! It's disheartening to discover such things after buying a car. I feel for you. Probably the cheapest fix would be to grind off as much rust as you can (down to bare metal) and drap the area with thick fiberglass mat drenched in resin. The mat I am referring to is about 1/8" thick, not the thin weaved stuff. My buddies and I did this type of repair in the past and it held up as long as you maintained an oily undercoat underneath after the repair was completed. If not, water can get between your repair and the remaining metal and cause more corrosion. It might also be advisable to apply a thin mist of rustproofing compond on the inner side of your repair. Usually the carpet has a backing that would serve as a barrier to the carpet fibers. Ideally, you would weld in a new floor pan, but you could probably find someone to patch it with steel strips/plates. Regardless of which approach you take, I would intermittently apply a non-drying rusproofing compound. Good luck and please document the process and post pictures of your repairs if that's possible.

Pic of the mat I'm referring to. Lots of vendors on eBay but you could probably source locally:

https://i.imgur.com/5tUhc3q.jpg

[ex-x-fire]

Best bet is to cut out the rust and weld in new metal. You need to treat the other spots too. I like fluid film. Anything will be better then nothing.

[Spellino]

That's nasty! It's disheartening to discover such things after buying a car. I feel for you. Probably the cheapest fix would be to grind off as much rust as you can (down to bare metal) and drap the area with thick fiberglass mat drenched in resin. The mat I am referring to is about 1/8" thick, not the thin weaved stuff. My buddies and I did this type of repair in the past and it held up as long as you maintained an oily undercoat underneath after the repair was completed. If not, water can get between your repair and the remaining metal and cause more corrosion. It might also be advisable to apply a thin mist of rustproofing compond on the inner side of your repair. Usually the carpet has a backing that would serve as a barrier to the carpet fibers. Ideally, you would weld in a new floor pan, but you could probably find someone to patch it with steel strips/plates. Regardless of which approach you take, I would intermittently apply a non-drying rusproofing compound. Good luck and please document the process and post pictures of your repairs if that's possible.

Pic of the mat I'm referring to. Lots of vendors on eBay but you could probably source locally:

https://i.imgur.com/5tUhc3q.jpg

Thanks for the feedback. However, this is the first time, since I've owned this car, that I feel like I can't DIY.

[Spellino]

Best bet is to cut out the rust and weld in new metal. You need to treat the other spots too. I like fluid film. Anything will be better then nothing.
I guess it means a trip to the welder

[06YarisRS]

I guess it means a trip to the welder

Probably the best bet. However, if you want to DIY, fiberglass offers an excellent, non-rusting, alternative to welding in steel. Any steel you weld in will still be subject to rusting - especially where welded - and it can be harder to ensure a water tight seam when welding metal in. Personally, if it were my car, and I was trying to save money, I would go the fiberglass route. In either case rust removal, and maybe conversion (phosphoric acid) would be sound preparation. Whichever approach you take, I would absolutely avoid putting any kind of rubberized (drying) undercoating over your repair. That is simply asking for water penetration and accelerated rusting.

Ex-x-Fire makes a great recommendation in rustproofing product. Fluid Film is an excellent and relatively long-lasting product.

Best of luck. And please document if you can.