Evapo-rust vs phosphoric acid

I have the plumbing apart in my Perkins T6.354. The exhaust manifold has some orange- black crud in it. I'm contemplating using Evapo-Rust to clean inside the water jacket. Which do you think is the best chemical? It seems there are two types: phosphoric acid or a chelating agent (Evapo-Rust).

Also, which approach is better:
Fill it and let it soak, or
Setup a bucket and pump to circulate the chemical.

Lastly, is there any value in using a rust converter after the chemical cleaning process? This is the type of chemical that turns rust into some kind of inert compound, like Rustoleum Rust Reformer. I could fill the water jacket with it and then let it drain from a plug at the bottom.

A review of Evapo-Rust rust remover

https://ncptt.nps.gov/blog/comparative-study-of-commercially-available-rust-converters/

Thanks,
Robert

I'm restoring an old E-type Jaguar and have used both Evaporust and phosphoric acid extensively. Phosphoric acid won't work very well for what you're doing as it doesn't penentrate...it forms a hard phosphate layer over the top of moderate to severe rust and that's about it. The rust still lives under that outer shell. Yes, it converts, but just that outer "shell".

I used Evaporust on the sheet metal including the doors, which were dipped in a large heated commercial vat. The surface must be kept wetted. Also, the liquid "wears out" as it becomes saturated with rust particles. So, you want to scrape and chip as much rust as possible before using the chemical. Also, be sure the crud is indeed rust and not calcium deposits. I scraped the big chunks off the inside of the water jacket on my jaguar block, then plugged all the openings and filled it with Evaporust and left it out in he hot sun. A lot of crud came out in solution when I drained it. That said, it's best to circulate the stuff as it carries off rust particles and exposes new surface for the chemical to attack. You can see from a couple of attached photos that it really does work. The body shell was cleaned with a garden hose/fan shaped spray/sump pump. Again, the surface must constantly wetted (a possible problem with circulating inside the engine). Final thought...it's more effective when warm...I had a heating pad under the reservoir when I was flushing/spraying it into void areas like rocker panels.

The converters are basically phosphoric acid. There's no point in using any of the converters inside the engine.

Nice Jag! Good luck with that project. Are you posting updates as you go somewhere?

And I agree with what you said about flushing the engine. You could use Rydlyme or Barnacle Buster as well.

Acid cleaners and chelating cleaners work entirely differently. I am a little surprised that the PP had better luck with the chelators as they are much milder acting than phosophoric acid. The real advantage of chelating agents is that they can be combined with alkaline degreasers to remove grease and cut rust with one cleaner.


Phosphoric acid should work about as good as anything on your manifold. I think that filling and dumping every ten minutes over a two hour period will do as good as circulating the solution. When you dump, leave it about 1/4 full and shake it to slosh the solution around and break up the surface deposits.


David

Capt.Bill11 said:

Nice Jag! Good luck with that project. Are you posting updates as you go somewhere?

Click to expand...

No, but at the risk of going off topic, here's the current state of the project. Engine should be ready to insert in a few weeks. Last photo is the objective (same color in sunlight).

Congratulations! Very nice work. Flat out the sexiest car ever. Hard top or convertible.

Now you need to restore a second one to drive while one or the other is in your shop.

I'm impressed. You filled a commercial vat with EvapoRust? How long did you let the doors soak?

No, a local metal rehab shop has a huge vat where they can dip entire (stripped) car bodies and anything else that is not greasy. The chelation chemical will not touch sound paint. I'd guess the doors were in the tank about two days. Attached photo better illustrates how I did the tub section in the garage. The blue bucket is five gallons of Evaporust...about $80 at Northern Tool. I used ten gallons for the tub, bonnet, and engine plus miscellaneous smaller hardware, etc.

Is the crud a sludge which needs cleaning? If so, you could use Extreme Simple Green or Grease Lightning and a wire brush to clean it out. Rinse with water and let dry after which you may see a light coating of rust in there. Proper coolant will have a rust inhibitor (it does need to be changed at appropriate intervals to maintain this protection), but to get a head start on protection, you could spray the dry rusty surfaces with a rust-killer. If the surfaces are clean and free of rust, just reassemble it and let the coolant's rust inhibitors do their work. After all, the rest of the engine's internals exposed to the coolant are also bare metal.