How to treat this corrosion?

Hi all, pretty new here, finding loads of useful info.

My 2007 Jimny is pretty clean overall however there is a spreading patch of corrosion on the rear panel next to the driver's door. I removed a paint bubble there a couple of moths ago, scraped off the rust and loose paint, and painted over with touch-up. As expected though it's breaking through again. Used to be a product called Trustan that was great for killing rust like this but it's no longer available.

Any suggestions?

There seem to be a good few articles here on rust - search "Rust"

I'm restoring a 1930s vintage car and use a product found easily on Amazon, called AQUASTEEL . Its used on awkward difficult/places where wet and salt are of a concern such as oil-rigs.
There is a NATO stock number for it as well, so it seems the military use it too, and for that it would have undergone a lot of trials

I've used it on rotten quality steel garage hinges and the rust has gone for good, as well as my 80 year old car that was simply a pile of rust and is now a gleaming chassis.
The beauty of it is that unlike an acid based product that needs rinsing with water (which to me seems a bit counter-productive) you simply brush this on and the rust turns blue/black and you can then paint directly onto it.

In five years of using this in various rust-situations I have not had rust return. I'd also like to point out that I am no fan of so-called ' rust conversion' products and would much prefer to grind out corrosion properly until any of the rust-worm cannot be seen even under a magnifying glass, then properly etch-prime and paint, however this is one product that I have been super-impressed with.

There are is a lot of support in the forums for a product called Buzzweld which interests me greatly too. I'd never heard of them before but they seem to have a good reputation here.

You need to treat the area with a rust stabilising product or remove all the rust before you paint. Hammerite Kurust available from Halfords etc is a similar product to Aquasteel in that it converts the rust into a stable layer ready for painting. Machinemart do an acid based product (Clarke rust remover product 059930250) that removes the rust, but you don't have to wash with water after treatment which I also think defeats the object.
For that area the acid product would be my preference, the converters are good for hard to reach places or chassis etc.

You may need to remove the plastic side panel to get at all the rust, its likely its made it behind.

Once treated, prime and top coat as per the paint suppliers instructions.

Never seen one rust in this area
If it was mine i would find someone breaking one
And get a section cut out and get it welded in

Only times i've seen rust ther on cars, is if the doors badly adjusted and catching the panel or it's had a front end smack and pushed the door back into the panel.

Mine has a little bit of rust here. I think its caused by the seatbelt not going back in properly, then getting shut in the door (at least thats whats caused mine).

I had this thing on both sides and it is simple - it's a crack in metal, it needs to be welded and painted. Probably caused by vibrations and large flat surface area behind it, at least my "tinman" says so and I trust his oppinion - he had his workshop for the last 40+ years and saw this thing few times.