924Board.org

[safe]

I'm not a big fan of manual labor for removing rust, so if possible I choose an easier path...

My 931 has had a lot of rust that I've fixed, not as much as the Rat rod...

The left fender was to much work so I got a "new" one. The right has some low down, but its a bit crusty on the inside.

So I mixed up my new favorite rust eater and dipped the fender in.

This is after one day, It was a bit old and not enough. So I made some more.


Here is after 3 days and scrubbing away the residue. There is a clear line where the level was.




The solution is really mild on the steel, but takes a few days to remove the rust..
Its Citric acid with Sodium carbonate so its not as acidic as straight citric acid. But it doesn't work on the acid-principle, it works the same as Evaporust, the word escapes me right now.... Edit: chelation https://en.wikipedia.org/wiki/Chelation
But its really cheep so you can whip up 100 liters (26 gallons) for ~$100 .

This is going to be metric....
10 liters of water
1 kg of citric acid
300g of sodium carbonate
+ a little dish soap, not sure why but I guess for surface tension.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[morghen]

Great, thanks for sharing.
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Supercharger and EFI kits
https://www.the924.com

[fiskolja]

Perfect timing!
Have been looking at doing this for a while and had previously decided to try it this evening, although on some smaller parts but the principle should be the same.
Also been looking at setting up an electrolysis solution but will try just citric acid and sodium carbonate before I get my hands on some sacrificial anode.

Where did you buy the pulver? Have been looking at Kryddhusets citronsyra and bikarbonat från ÖoB
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924 NA 1977

[safe]

[fiskolja]

[safe]

The carbonate is only there to neutralize the aciidity in the citric acid. It will probably work better without it, just a bit harsher on the good metal.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[safe]

Found my youtube source:
https://www.youtube.com/watch?v=fVYZmeReKKY

Also found an independent test:
https://www.youtube.com/watch?v=DBzxiuGp5LA


You will need twice as much baking soda. And be careful when you add it.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[fiskolja]

Yes, I'll have good marginal in the container, good ventilation and a gas mask to not take any risks

Also found one guy that turned the solution in to a gel, practical for bigger stuff still assembled to the car:
https://www.youtube.com/watch?v=Gi4DqtpYAOI[/url]
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924 NA 1977

[Raize]

I wish there was a chemical way to remove the residue or at least make it overpaintable.

I've tried with phosphoric acid and ascorbic acid, basically the same result from both acids.

I tried electrolysis as well using stainless steel plates as anodes which was useful because they didn't corrode away like regular steel plates would. But it was just as annoying to remove the residue and did suffer from the "line of sight" issue.

[safe]

The "dirt" has to go somewhere. A lot of it gets suspended in the solution.
I've had the idea of filtering the solution continuously to see if that helps, I think it would do, but haven't tried it.

The easiest is to just degrease the parts and hand them of to someone for media blasting and powder coat.... That assumes that the parts are suitable for media blasting.

I've media blasted a lot of stuff my self in a really good cabinet with industrial compressor, but I hate it, a lot more work than you would think.
In a production facility they hang the parts on a rack and it goes thru a machine that does the blasting. But it costs a lot more if you are paying full price.

I've done some DIY zink plating too, pretty fun, but its also a lot of set up and trial and error fine tuning the process.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe