The floor pan on my Honda Jazz is starting to catch rust. Attached a couple pics under the rear (magic) seats.
Hoping to receive a few tips on my plan.
1. Remove as much of the rust (flakes and surface) as possible with wire brush and emery paper.
2. Give the rusted areas one coat of Rustoleum Rusty Metal Primer.
3. Give the entire floor pan a coat of the Rusty Metal Primer - i.e. a second coat for the rusted areas covered in 2.
4. (optional) Coat of paint primer.
5. Top coat of white paint.

Also, what exactly are the red-marked areas? Is it galvanized steel? I’m guessing this area should not (need not?) be coated? There are no signs of rust on it – just a few dust marks and carpet wool.

I will be removing the front seats as well to check for rust. Now, while I was trying to remove the carpet under the driver seat, I noticed a slim wire harness attached somewhere under. Just wondering what is this wire's purpose, since the seats are not ventilated, and there is no seat height adjuster.

 

Depending on the age of your car, that's pretty minor and entirely cosmetic (i.e., unlikely to cause a problem).

For example, if you told me you live in a salt area, regularly carry rear passengers, and use fabric or no rear floor mats, I would expect a bit of rust to form on the floor over time from moisture and salt transferred in on winter footwear.

Your remediation plan seems reasonable to me, although I don't know if I would bother with the second and third coats of primer. The areas outlined in red are factory sound-deadening material. Does it feel a bit rubbery? That's what I had in my 2010 Fit. Trying to remove it is a pain, so when I added supplemental sound deadening material I just went right over the top of the factory stuff.

The wire harness (actually, I think there should be at least two clips) under the seat is for the SRS system and side-bolster airbag, along with the seat belt warning light and, for the passenger seat, the front airbag deactivation sensor). Before messing with the seats you want to unhook the 12v battery negative. Then you can unbolt the seat and lean in backwards to access the clip(s) for the wire harness. If my memory is working, it was a pain to unclip on my 2010, and you definitely don't want to break it so take your time.

Another note, to fully remove the carpet you have to first remove the center console and will also have to cut a small section of carpet underneath the dash near the firewall.

 

Pic Assist

 

Thanks a bunch cb400bill.
It actually seems like metal. I thought it might be to structurally strengthen the monocoque structure.
From AI - "The Honda Jazz (or Honda Fit in some markets) utilizes advanced high-strength steel throughout its floor plan and chassis to balance structural rigidity with reduced weight.
Reinforced Floor Pan Components: The floor structure includes stamped steel parts for:

• Side Panels/Sill Structures: Strengthened for side impact protection.
• Floor Panel Sections: Front and rear structural reinforcement.
• Inner Wing Panels: Contributing to overall chassis rigidity."

I will remember to disconnect the negative lead.

It's funny actually we don't have passengers most of the time - just luggage. But yes, we live in a coastal area with heavy seasonal rain. It's nearing 15 years.

I was hoping to avoid removing the center console altogether. A pain to remove from the sight of it. Where are the seat rails in your picture? Were they removed?

 

Not sure if you were directing this question to me, but the seat rails remain attached to the seats. Four bolts hold them to the floor and the seat + rails come out easily.

I can't remember all the particulars, but the center console was not difficult to remove. Actually, the Fit/Jazz is well-designed to be serviced and worked on and have interior trim removed and replaced. The key is getting the service manual so that you can see how the different pieces of interior trim are attached and know how to (safely) remove them without breaking.

If you don't want to remove the center console, you can probably "roll" the carpet from the outside sill toward the center console. I'm pretty sure this will still require that you remove some of the plastic trim: kicker panel, side sill strips, etc.

As I mentioned in my first post, the areas you outlined in red are (or were originally) a sort of dense rubbery material, presumably for sound deadening. In an older car they very well may not feel rubbery anymore, but at least in my 2010 Fit Sport they are definitely not metal.

 

Thanks @Drew21 Sorry, meant to address the question to you.
I think I'll try get the center console out. Rolling up from the sides won't work.
Will have a closer look at those areas.
Looking out for a copy of the service manual.
Thanks much.

 

There was a copy of the manual on here, ready to download. Don't know if link is still available.

 

On closer inspection of these sections, tapping with a wrench etc., they do seem to be a kind of dense material, maybe not metal after all. You mentioned earlier you were trying to remove them. Did you have a corrosion problem or was it just for supplemental sound dampening?

 

Nope, no rust. Just adding sound deadening material inside the car.
I didn't try to remove the factory material, but one of the quirks of being slightly inbred from the Ozarks is that I am predisposed to poking at things with fingers, putty knives, screwdrivers, etc.

 

Relieved I won't have to dig them out.
Btw, those under-seat harness clips are a total pain. I left them alone. Don't want to mess with airbags. Any case, after checking cosmetically for rust under the seats, there isn't a trace. It was confined only to the rear seats for some strange reason. I think the vapor barriers gave way? I checked the rear wiper washer line that passes all the way along the door sills. That seems fine - no leaks. So the only way water (moisture) made it's way in is through the door. Bad design.