Removing surface rust on small parts.

I've heard Vinegar...
dropped a few small carb pieces in a Helluva Good Dip tub this eve...
See what happens....???

 

Yeah vinegar will, and works even better with some citric acid powder mixed into it.
I use a solution of white vinegar and citric acid as an engine and radiator flush,
the only downside is it works that well that any parts that are not 100% and may be actually still holding together with rust, will start to leak, I flushed a water cooled ZX900 Kawasaki motorcycles cooling system a few years ago and it exposed a weak link in the form of a metal pipe that carried coolant started leaking.
But better it did it in my workshop than 6 months later out in the outback near woop-woop.

 

OZ, This one guy has a video of wrenches and saw blades he put in Vinegar and forgot about for 17 months...
Most were partly or totally disintegrated....

 

yeah I put a handfull of nuts n bolts from a car I stripped down in vinegar and left them in it for months and it ate away at em!
So beware leaving stuff in too long!!!

 

The molasses only chelates the iron oxide, as well as converting FeIII to FeII (rust to an iron ). FeIII is not water soluble, whereas the FeII is water soluble.

It won't damage "good" iron.

Iron becomes FeII state, and then the FeII becomes FeIII (rust state). The molasses returns the FeIII back to the FeII state (iron ferrite or "black iron" similar to phosphated state) and is also why "derusting" in molasses results in "flash rusting" when the part is removed and cleaned.

I remove the item from the molasses, use a nail brush and pressure washer to clean the part, then wet it with prep-all to help shed the water and heat air gun to dry the part.

Then spray Ospho to deal with the flash rust, and when dry, re-wet with Ospho, and while wet (re-activating the acid) rinse to neutralize the acid and then hot air dry again, wash with prep-all (since my hands touch the items during the previous processes) and after that, prime and paint.

While it seems like a lot of work, the time spent using media blasting, or wire brushing, and several neutralizing and rust removal steps, the molasses bath and follow on, give great results.

And much less cost than Evaporust, and "safer" than acids. (Evaporust is not an acid. It is also a chelation process, much the same as the molasses, but likely a bit more refined solution.) $15 for 20 gallons of molasses, vs $20 per gallon of Evaporust.

 

Thanks TM...how long do you soak the parts in the Molasses?

 

Pair of 1965 GS manifolds in a 20 gallon aquarium, 2 gallons of feed grade molasses (needs the sulfur) and 18 gallons water, for one week. (about 9:1. 9 parts water/1 part molasses)

They came out nearly 100% clean. Looked like fresh castings.

I pulled them out, scrubbed them with a "vegetable" brush (looks like a nail brush, but a bit bigger), then put them back in for a day.

Pulled them out and hit them with the pressure washer.

That was to get the black iron sulfide off the surface, then followed with the other steps I mentioned.

If one were doing a block, or other heavily rusted part, it might take a few weeks.

The solution will ferment, so be mindful of the smell. I did mine outside. If you do this inside a shed, garage or other similar enclosed area, be prepared for the odors...

One can get a small jar of sulfured molasses and give this a shot with some rusted bolts. Once you see the effects, it will make an impression.

 

Evaporust is re-usable. I have been using the same 5 gallon bucket of Evaporust for 15 years now. It also has no objectionable odor, almost none at all. Mine is starting to slow down, so it may be time for a fresh bucket.

 

Baking soda goes hand and hand with vinger. It must be used after vinger bath for the chemical reaction to stop.

 

Didn't know it was reusable, that's cool.

 

Michael, Ospho= Orthophosphoric acid. Is that close enough to plain phosphoric to work the same?
I'm a long time user of Picklex but it's gotten very expensive these past few years. Len at http://www.autobodystore.com/ highly recommends the stuff. Great forum they have there. Brian Martin, brother of Nailhead guru Russ Martin is a regular contributor as well.

Where do you get the molasses? I have a local Tractor Supply but it's $8/gal, or about half the cost of Evaporust.

 

Opsho is about 75% phosphoric acid and also has small component of chromium salts (hexavalent).

I got the feed molasses from Tractor supply. $6 and change per gallon.

But you cut it 9 parts water to 1 part molasses. Or 20 gallons for less than $15.

20 gallons of evaporust would be $400

And treating something the size of exhaust manifolds with evaporust would be quite a bit using evaporust or similar.

Using acids, or caustic compounds sacrifice "good" iron/steal, where things that work be chelation remove the oxidised component and leave good material alone.

It takes some extra effort, but I think the benefits are worth it.

And "predictions" were that it would take several weeks to a month, but it was complete in a week.

 

Got it, Thanks! Mo-lasses is on my shopping list.
I'll guess temperature of the solution will affect the speed of the reaction. Warmer=faster.

 

Yes. Be aware that the sugars and sulfides will be "happy" and getting busy, so you want to do this outside.

I keep the tank covered to keep critters from swimming in the Loch Mess.