Are the Prius prone to rust at the lower front edge of the front doors?

All I can suggest is more/better cleaning there during the winters.

They rivet the speakers in because it's inexpensive and rattle-proof vs. most other fastener types. That's important for a speaker.

 

I was gonna say due to neglected scrapes, but that looks like spontaneous bubble up, not at a lower (vulnerable) edge.

 

Just speculating, it kind of looks like puddle water/runoff is getting pulled into the gap at the leading edge of the door. That's outside the door seal gasket, so there is airflow in that door jamb area.

 

Doing what you propose will mean that you are only removing and covering up the surface rust. Like and iceberg, the rust originates from inside the door at the seams. You have to remove the door panels and coat the rusted seams wit rust converted that chemically changes the iron oxide to an iron phosphate. After that, I would coat these areas with a light petroleum based rust proofing like LPS3.

Then, after the treatment fully congeals after 60-90 days, I do the treatment that you propose.

From my dad's years of experience with cars of the 1960's with every car I purchase, I fog the interior bottoms of the doors with a light rustproofing like LPS3. Eve when the metal is factory rust treated, any sharp edges from crimps or tool marks on the steel will promote corrosion from either condensed or water flowing down the outside of the windows. The water drains out the weep holes on the bottom. If they are not clear and blocked, water will seek it's lower level by rusting out the thin metal.

Rustproof has a bad reputation, because it is seldom done right. The joints of the seams and contact with panels and fasteners are is where rust begins. Filling these spaces with rustproofing oil keeps the water and salts that make electrolytic corrosion from happening later than sooner.

 

I'd get a body shop to remedy it, do a thorough remediation. Any cosmetic outside treatment will just bubble up again.

 

If you really want to get in there, just drill out the rivets. The rivets are soft aluminum, just a few seconds of drilling for each, and you can rivet the speakers back in with a $10 kit.

It was no big deal to do that when I swapped my speakers for nice aftermarket ones. Just use a short drill bit so you don't accidentally dimple the door skin.

 

Using an aluminum rivet of a steel panel is not ideal and will promote rust, Use a steel rivet.

 

I can't swear that what I drilled out was aluminum, but it yielded to the drill so easily that it was my first guess.

 

How does it look today I got same issue on right back door but more in back area and drivers got a lot of bubbled up paint