Killing rust….suspension pan.

[Balisong]

Hello
Here is a pic from a borescope of the fuel tank support area.
The car is very low miles and mint but the long term original owner used a battery tender that led us here.
I’ve already done a baking soda water flush (2 actually) to kill any remaining acid but this rust is left behind.
I’d like to flush it one more time with a rust killer product and then perhaps finish with a cavity wax or primer.
Rustoleum makes a rusty metal primer but it says not to use on galvanized steel.
I’ve used POR before but I’d like to use something that will kill the rust and let me inspect it before I primer it.
Any suggestions appreciated.
Tempting to widen these drain holes to assist with the cleanup but the car is too original to modify.
Thanks!

[Balisong]

Borescope image inside that cavity.

[BK911]

Phosphoric acid from the FLAPS.

[Locker537]

Fluid Film

[john walker's workshop]

Rust never sleeps ya know.

[Balisong]

Was watching this

https://youtu.be/LlZaTzXqp3k

and it seems like since I can’t do any physical scrubbing on the area (because it’s enclosed) I’m thinking phosphoric may not remove the rust.
Muriatic acid would probably do the work but obviously it’s dangerous, fumes cause rust on other parts, etc.
Considering this approach:
Muriatic acid bath
Follow up with Vinegar bath to neutralize
Finally Corroseal bath which will cover the metal in primer.

[1989Carrera]

Look into Evapo-Rust. You need to keep the infected area soaked in Evapo-Rust to get the best results so you'll need to block those drain holes.

https://www.evapo-rust.com/

[BK911]

Phosphoric acid is a rust converter.
Soak really good several times.
Then coat with por 15 or equal.


Phosphoric acid is known as best rust remover on the market. It acts quickly on rust and is not overly aggressive on underlying metal. When the solution in liquid is placed directly on rusted areas of steel, steel tools or steel surfaces, the rust is converted from the red oxide to a black ferric phosphate.

[2.7RS]

Car Cancer
Get a car surgeon

[70SWT]

Originally Posted by 2.7RS

Car Cancer
Get a car surgeon

+1. If you can't grind or cut it out, it will come back. Chemical treatments can't adequately handle rust when it is more than light surface rust, in my experience.

Then there is the issue of rust down in (at least parts of) the seams that the chemicals won't necessarily even touch.

I would just replace the affected front pan areas and be done with it. This has been almost a rite of passage on most pre-galvanized 911s I've owned and some later ones. It usually depends on whether the history includes prolonged sitting with battery leakage.

[targa72e]

Evaporust works very well, doesn't smell and is not caustic. The issue will be keeping the area saturated. There was a person (on 914world I believe) that wanted to do something similar to remove minor rust that was inside of some body cavities. They rigged up a way to flood the areas continuously with the Evaporust liquid. They put a tarp under the car to collect the evaporust that drained out of the car and sloped the tarp to a central container. They used a pump and hose from the central container to pump evaporust to the area to be treated. By plugging the holes the area totally filled with Evaporust liquid. Then they just Let the pump run circulating the Evaporust and keeping the area full (I believe they let it run all day). When done no rust was left. After that treatment you could treat the area with sealer to keep rust from coming back.

john

[mepstein]

Most of the time when the inside of the front suspension pan is rusty, it’s just an aluminum foil thickness from turning into Swiss cheese. Use a pick and make sure it’s solid and not just held together with undercoating.

[Balisong]

I got another closeup and it may be better than I think.
One thing is for sure….the panel is strong so I do not want to replace it yet.
It’s now soaking in EvapoRust so tomorrow I’ll check it again and see how it looks.
Thanks for all advice.

[Balisong]

Changing a bit after 20 hours.
Filled it back up with EvapoRust and will leave it till Sunday.
Once I’m done with the rust treatment will it be ok to just wax the cavity (like fluid film) or do I definitely need to prime it. I’m a little uninclined to use POR because all I can do is pour it into the cavity and drain it out…no way to brush it on.

I’m inclined to used Corroseal (primer) or just a cavity wax.

Thanks!

[Balisong]

EvapoRust did a great job after about 40 hours.
Coating it with Fluid Film now.
Pretty happy with the result.
Thanks all