Rust on the door – removal
 

Some guys have this problem.
The bottom of the door is rusty.
The cause of the problem is most likely a bad rubber seal. There may be another reason, but this is not important yet.
Today I finally decided to kill my rust. I got tired of it.
Therefore, a few pictures, if I may. I would be glad if my experience will be useful to someone.

And so: good sunny weather, a day off, started ...
I did not photograph the rust directly - everyone saw rust.
I just took the sandpaper into the hands and began to scrape away the friable oxides. From time to time I washing off the dirt with soapy water.
I used the first available Sandpaper, it turned out to be pretty coarse. This is not bad, rough sandpaper with a large sand speeds up the process.
After 15 minutes, I received the remnants of rusty bloom and glimpses of bare metal.

Next, I used chemistry.
Phosphoric acid (H3PO4) is the basis of most rust conversion agents. I specifically bought it. Acid is cheap, but it works fine, and you don’t have to overpay for beautiful packaging.
Now I must apologize ... I do not know American life, perhaps phosphoric acid is not for sale in America or is sold under a different name. The bottle (you see it in the picture) I bought in the store for radio amateurs in the section "all for soldering". Further, I also use products that are sold in Russia, but in the US there is the same or analogs.
https://cimg5.ibsrv.net/gimg/www.che...4c74f9e52d.jpg

I fiddled with acid for almost 2 hours.
So the technology is simple: you apply acid to rust, smear it with a brush and wait 15 to 20 minutes. At this time, the acid eats rust. The acid has a thick texture, similar to a clear sugar syrup. Wait a little, ride the acid with a brush, correct the result with sandpaper, add acid again.
https://cimg1.ibsrv.net/gimg/www.che...295ee405cd.jpg

Acid tingles the skin, but does not burns. I worked with bare hands, but someone sensitive should use gloves.
As a result, I received a bare shiny metal with no signs of a rusty color.
https://cimg4.ibsrv.net/gimg/www.che...8b40e620e5.jpg

https://cimg1.ibsrv.net/gimg/www.che...9b2222c544.jpg

I washed away the acid when rust was destroyed.
I used soda to neutralize the acid. I just went to the kitchen and took the soda from my woman, she uses it for baking.
I poured some soda into the water and washed the metal with this water. I used about 3 spoons per 1 liter of water, but I do not know the exact dose. Just poured as much as the right hand wanted. I washed the surrounding surfaces with the same water, otherwise the dust would prevent the protective paper from attaching.
https://cimg8.ibsrv.net/gimg/www.che...f144a14cb6.jpg

The next step is painting.
First you need to separate the painted surface from those places that do not need to be painted. For this, I used paper masking tape.
The tape and the old newspaper, that's all you need. But for me it was not an easy job. I do not know why, but it turned out to be the most difficult part of the process for me.
https://cimg8.ibsrv.net/gimg/www.che...cf40e9c195.jpg

https://cimg4.ibsrv.net/gimg/www.che...796a5b12ee.jpg

When the protection is glued, proceed to the second step. It is necessary to protect the metal from corrosion. For this, I used the "acid primer"
https://cimg5.ibsrv.net/gimg/www.che...dd342d26ab.jpg

This yellow substance penetrates into the upper metal layer at a low molecular level and protects it from further corrosion. At least, so the car painters told me (I hadn’t done anything like that before, so I consulted with the professionals).
https://cimg2.ibsrv.net/gimg/www.che...2817d0dec1.jpg

After the acid primer is dry, it is time for ordinary primer for subsequent paint application. I used this ...
https://cimg4.ibsrv.net/gimg/www.che...7e157e2d0e.jpg

here is the result of its use. Light gray smooth surface.
https://cimg4.ibsrv.net/gimg/www.che...7013374bc5.jpg

https://cimg3.ibsrv.net/gimg/www.che...c04f454139.jpg

I used nitro enamel for painting. I ordered the paint in the laboratory, specializing in the selection of car enamels. I must say, I did not use the spectrometer to not pay a lot. I just picked up a GM color catalog , went to the car and chose the most suitable color. The color is certainly different, but not much. I would not use it for painting exterior panels, but it is suitable for painting the inner edge. Moreover, no one looks there.

What happened next is a pure gamble. I do not advise to act like me, but this is what I did: I did not dilute the paint, because I did not have a solvent. I also did not have a spray gun or even a decent brush. I just took a fence brush, dunked it in paint and painted it at my own risk. When the paint dried - did it again. It turned out 2 layers of paint.
https://cimg8.ibsrv.net/gimg/www.che...d4ed7e9a74.jpg

https://cimg4.ibsrv.net/gimg/www.che...acb1aa9b68.jpg

https://cimg8.ibsrv.net/gimg/www.che...b86676c487.jpg

Of course, the paint is uneven. Clearly visible stripes.
Next, I intend to polish to bring the painted surface in a satisfactory condition. But more about that next time.

If it's interesting for you, my rust removal costs.

Of course, I paid rubles, but for your convenience I specify the price in US dollars.
1. Phosphoric acid = 1 USd / bottle;
2. Nitro enamel with selection service = 10 USd / 200 grams;
3. Acid primer = 8 USd / balloon;
4. Ordinary primer = 7 USd / balloon;
5. Masking tape = 0.5 USd / roll;
6. Brush = 0.3 USd / 1pcs

And of that: less than 27 USd

Time spent is half a day, incl. shopping spree and advice by phone.

Preferred popular, but cheap products.

Nice write up, thanks for taking the time to document your work.

Looks good. Didn't know the acid would remove rust like that

Hey, what a fun project. I've had to do a few like that over the years, and found them fun and interesting. It looks like you took your time, and prepared everything well.
Good job man - and thanks for the pictures.

Here in Canada we have quite a few of the equivalent products:
(this is just a list of products that are commonly available here - not a recommendation for their usage)
- Rust remover - https://www.canadiantire.ca/en/pdp/r...7924p.html#srp
- Rust converter - spray- https://www.canadiantire.ca/en/pdp/r...7965p.html#srp
- Rust converter - brush on - https://www.canadiantire.ca/en/pdp/r...7964p.html#srp
- Rust preventer - the infamous POR 15 - hard to find/expensive/great reputation - https://www.canadiantire.ca/en/pdp/p...5874p.html#srp

Often the rust on the bottom of the door is caused by the door skin wrapping around the bottom frame of the door, and collecting moisture from INSIDE the door.
So you might want to check out the status of the inside of the door at the bottom, and perhaps use something along the lines of this inside the door to protect and
clean up the lower seam - https://www.canadiantire.ca/en/pdp/r...7985p.html#srp

I am pleased that my artisanal work deserves your positive feedback.
thanks
About orthophosphoric acid ... I see that you are interested in its use. I wrote a little about it, but here is the link: https://en.wikipedia.org/wiki/Phosphoric_acid
Please pay attention to the prefix "ortho", I used exactly that. This variety uses Coca-Cola Co. for the production of beverages. And it is used when soldering under the name "flux for soldering".

You never used Naval Jelly ?
https://www.walmart.com/ip/LOCTITE-N...l3=51779630471

In the USA it is called "Naval Jelly". Sold by many brands; Loc-Tite, Rust-Oleum

You can simply use straight Coke

Actually, in that location, I wouldn't get too carried away with beauty. You did a real nice prep job, and that is the big key to success. We have self-etching primers available here (US) that might have saved you a step, but your steps were all good until paint application. You know that. Did you clear-coat it? Maybe you want to fix it, but a clearcoat is so important that waiting is not a great idea. Overall, I give you an A.





Used to work in Manufacturing Engineering at GM in Paint...