[QUOTE=Zacharias;3210351Why not just cover the surface in vinegar then pour on some baking soda? Works great for drain clogs, including hair, and I cleaned stubborn stains off an old white enamel sink that way.[/QUOTE]

You could probably clean the area ok but the fine grit of the baking soda is better for cleaning than the foamy mechanical action of it with vinegar. It works so well on sinks because the vinegar breaks up the carbonates from hard water.

As for the chemical action of becoming iron phosphate, baking soda won't cut it. It is a carbonate molecule. You might be able to get something with baking powder as it is sodium phosphate but that winds up being very expensive. It still may not reduce the rust and turn it into hard iron phosphate though since it isn't in suspension and is a base. The phosphoric acid of colas is what you need for metal etching as everything you need is in suspension but they would take a while since they aren't as concentrated as the commercial products.

I think for a small spot of cleaning metal, a few lemons would do just fine. They are great applicators themselves just being chopped in half or in quarters. That is strong citric acid too so it would work better than any store bought vinegar. 99.5% glacial acetic acid is available in gallon sized quantities from photo suppliers and is the highest concentration you can get but it is very hygroscopic and will always begin to absorb water from the atmosphere and dilute itself down to a stable concentration below 50%. If left uncapped to absorb water, the acid will increase in volume and overspill its container if left long enough. Many a darkroom sink and floor have been ruined this way due to not capping that bottle.

Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

To some extent this is true

Rusty surface, no oil:
You can wirebrush off any loose flaking rust, then paint right over it. That's why it's called PaintOverRust. I have done that for 20+ years and believe me it sticks!
Using a rust converter like their Metal Prep (the old name), now Prep & Ready will convert most of rust to a hard phosphate and do some etching to leave a good rough surface for the POR to stick to. Better job perhaps.
Of course if there is oil on rust, you need to get rid of it.

New metal
Get rid of any oil. I haven't found the Marine Clean very good and it is expensive. Maybe I diluted it too much. I use whatever I have - Simple Green works. Flush with water afterwards. If time is important, I flush with brake cleaner. Sometimes I use Varsol, before using Simple Green or similar.

Next, because no one sells Prep & Ready around here, I just abrade the surface of new or smooth metal (or painted surfaces) with power wire brush or rough emery paper. NAPA does sell a metal prep that would probably work.

Paint. I used to always use POR-15 and it is good. But NAPA in Canada sells DOM-16 which is very similar, but less than 1/2 the price. My 300D has a about a gallon of it on it by now!

Sorry for long post, but gist of it is that many times you can just slap the POR15 on over the rust (just painted my rusty exhaust that way!)

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

It's pretty much the same as POR-15. NAPA only sells black. ($18.00/pint vs $40 for POR) It is made by Dominion Sureseal - A Canadian company but sells worldwide. I also use their seam sealer which is rubber based.

See my post above about prep. It requires the same lack of prep as POR on rusty surfaces I would use any rust converter first if you want the best possible job. Use a metal etch on new metal or sand it rough so there is some tooth for the paint to grip onto. And get any oil off first before painting as you would with any paint.

When I first used POR, I don't recall them having all those add-on products! Just paint over rust

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I read a thread where a guy made plywood / 2x6 sides on the ground and lined it with heavy plastic sheeting large enough to sit his CJ-5 tube in. De-reusted it with electrolysis. Pretty impressive.

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You can't always get what you want, but if you try sometime you just might find you get what you need.

I wish I could do that to my friend's 280Z shell. Instead, we're going to have to settle for media blasting. I might do the doors and hatch in a big kiddy pool, however.

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- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Here is it is POR15'ed..



Here it is with the wagon swaybar installed... remind me to never ever do a w123 swaybar upgrade with the engine still in.

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1983 123.133 California
- GreaseCar Veg System

That would be a sight to see. Any links to that?

.

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1983 123.133 California
- GreaseCar Veg System

The nice thing about the electrolysis is when it works correctly it should pull the rust out of the seams where media blasting would only attack the exposed rust.

Didn't save a link, but you can probably google it. IIRC, he used an older stick style welder on the lowest setting as his DC poswer source.

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You can't always get what you want, but if you try sometime you just might find you get what you need.

I decided to try this on the rusted battery tray.

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1983 123.133 California
- GreaseCar Veg System

After two days..


After 3 days...


After 5 days...


There was a thick coat of rust on this piece, and it required several rounds of adding ketchup and vinegar, and a bit of scrubbing. Overall I am happy with the results.
.

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1983 123.133 California
- GreaseCar Veg System

Cool. Myth Confirmed

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http://i284.photobucket.com/albums/l...aman/Fleet.jpg

Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic

Some of the pictures are flipped over. Had me confused until I noticed that.

I realize this was just a test and interesting that it works. What it did for me, is confirm that Ketchup is something I should avoid

For an actual repair, you could just wire brush off any loose rust then paint with a couple of coats of POR-15 or equivalent. Where I have done that in past, it is still good after about 20 years. Treating with a rust converter before, no doubt is better, but not really necessary.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Sorry about the pictures all flipped over, should of corrected that before posting.
Regarding painting over the rust.. I read some posts in other car forums that when the poster painted over the rust with POR15, later down the road the finish started to bubble. They didn't really go into discussion as to what their prep procedure was, but I would bet they did something different as the coating did not seal off any air. Anyways, by removing the major rust, it prevents any of this thing from happening.

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1983 123.133 California
- GreaseCar Veg System

i have read the same about POR as far as flaking off.
BTW, thanks for posting this info on ketchup. it takes dedication to do the job right.
i had a neighbor that used to paste ketchup on all his food, including salad. seems to be the memory that always comes up when i think about ketchup.

April Fools day is not until 1st April. Your a few weeks early.. good joke tho. cheers