Have you seen anything like this?

Mine has the same line but no rust as well. Can you peel back the black paint at the line to see if there's rust underneath it? When was it built? Are you SURE it's never been submerged? How many miles on it when you bought it? Here's my '24 built in Feb:

 

I bought the truck brand new, purchased in April. Not sure when it was built.

 

Maybe you already know, but input your VIN here:

https://account.toyota.com/api/UI/L...udG95b3RhLmNvbS9vd25lcnMv&response_mode=query


along w/your 'As-Built' profile, it should also specify first date of service and if any maintenance services done by Toyota.
Hope this helps.

 

OP check this out
https://youtube.com/shorts/8JXvTav1XNQ?si=upsI9-syfWi_9_1s

 

I had a Ford work truck that looked like that, all rust up under the dash. I figured it was under water somewhere before I got it . Probably a hurricane truck

 

wow.. weird.
Could it be some type of powerful air freshener emitting a mild corrosive gas over time?
Maybe AC/HEAT system has a defective mix of refrigerant/coolant mixing in system somewhere?

 

That’s what I was thinking. I bought an old bronco with surface rust up underneath the dash and seats that looked very similar to the OP’s. The previous owner had a few and decided he could drive home. Ended up in a canal. I knew that when I bought the truck But that’s what it looked like underneath.

Strange that it would be on a brand new truck, but I’ve seen dealers do shadier things I know an Audi dealer that sold an R8 as ‘Brand New’ after the owners kid totaled it out joyriding and showing off for his lady friend. Not just bumped and bruised, but smashed every body panel and most suspension and steering parts; complete tear down and rebuild. I guess he didn’t want to claim it on the insurance and get the cops involved with the accident, so he fixed and pawned it off. He was legally able to sell it as new because it had never been titled, and the car fax was clean because they never reported the accident since the car was not yet titled.

Hopefully, though, it is something simple like the OP needs to run the AC more to dehumidify then cabin every day. Or stash desiccant sachets around the vehicle and replace them every so often, being near the beach.

Either way, that’s bizarre.

 

I'm thinking ozone gas generator used to remove foul smells out of vehicles.

 

If it’s a hybrid, could it be from batteries off gassing in the cab? moisture from a leak is more likely but….

 

Holy shit, that looks exactly like mine does. I am currently still fighting with Headquarters Toyota.

 

It’s a hybrid, so it’s definitely a possibility.

 

I have a very basic air freshener, nothing fancy. I don’t think it could be that. The AC/HEAT system theory could definitely be more like it.

 

High humidity, condensation (think AC), salty air, untreated cold-rolled steel living in a relatively air right environment....it's the perfect storm for surface rust, unfortunately.

On the bright side, surface rust usually doesn't alter the structural integrity of the parts. It just looks bad.

 

I don’t think the environment has anything to do with it unfortunately. I had a 2023 Tundra for a little over a year and never had any rust where this one has it. The other truck was kept in the same environment and same condition as this one. I have only had this one for about 6 months.

 

Has there ever been anything carried or stored inside your cab that could have put off any type of corrosive gas (like chlorine bleach tablets)?

 

I have a 23 platinum that had a leaking windshield for almost a year. Corrosion in some of the same places you have. Water wasn't visible until after a torrential downpour when it puddled up under the dash and came down on my legs when I started the truck. Water was running down the pillar and pooling under the floor mats and wasn't visible. Took the truck in 6 months prior to complain about a very musty smell and that I thought there was a leak. Dealer told me they checked everything and there wasn't any leak. I asked them to replace carpet and padding under warranty because of smell and mold but they have refused.

 

that’s definitely interesting, however I live in Florida so torrential downpours was the normal during the rainy season here and I didn’t feel any water or could smell anything. Not to mention that my seat rails are pretty far back from where your leak was.