Rust removal

[Carol Reed]

OK, guys and gals, I drug home some serious rust over the weekend. Pictures in a bit - different post.

Obviously I will need to do some serious de-rusting. Been reading about electrolysis. So generally speaking, an anode of iron, water, a plastic container, a battery charger, washing soap, and a few clips. Negative to the part being cleaned, positive to the anode.

But the devil is always in the details. So here are some questions.

1. There can be no physical contact between the part and the anode. If there is we have a welding process. Yes? There is an optimal distance between the 2, the most efficient being ~4'. Yes? A meshed plastic barrier is not a bad idea, but perhaps a good one?

2. The part has to be suspended in the solution, or can it be submersed and touching the plastic container?

3. Is distilled water necessary or can tap water be used if is not unduly high in minerals?

4. Lower voltage and higher amperage ought to be the settings. Yes?

5. Is TSP the same as washing soda?

6. How often do you remove the part, brush off the gunk to see when it is 'done'? Is overnight too long?

7. What do you put on the part immediately after cleaning and before painting and/or waxing to keep the thing from rusting again? Preferably a spray on product. I want to have a paint-able surface without having to remove something else later, if possible. I have low coastal fog to deal with.

8. Does the container have to be a bucket? I was thinking of a plastic concrete mixing tub (HF $7 and needed later for its intended purpose), a piece of rebar down each long side connected together, a plastic mesh barrier between the rebar and the part, and a few concrete chunks to rest the part on. Some of them are rather large, like a table saw table. What do you think?

9. What is the recipe? How much washing soda to how much water?

10. One item has badly corroded aluminum parts, to the point of pitting. How does one clean these up?

Thanks, folks.

 

[Darren Wright]

5. Is TSP the same as washing soda?

Don't have many answers for ya, but TSP = Trisodium phosphate, Washing soda = Sodium Carbonate.

I use Washing Soda for the pool, which is the only reason I know that.

 

[Ryan Mooney]

1. waves hands, I wouldn't stress it a whole lot as long as they aren't touching (not sure it would actually weld but it would certainly short out) and there is a clear path through the solution between the cathode/anode.
2. Submerged and on the plastic is fine, you might want to shift it part way through to expose the bits that weren't free floating.
3. tap is fine, remember the soda is to add conductivity so minerals in the tap water just help that along
4. amps are the thing that makes it happen so yep low v high a!
5. Darren got this one Washing soda is easy to find though, they have it at the local HD and Wally world at least. You can use baking soda but it doesn't have quite the efficacy (and sorry not entirely sure why) but works fine - do NOT use salt (or you'll chlorine gas yourself - someday in person I can tell you a bad story about that ).
6. smaller parts generally more frequently but about overnight sounds about right for a first pass for most stuff. After that I'd check it every couple of hours or so. You might want to knock the anode clean while you're at it as well as it will get pretty icky (and start to dissolve as well). You might want to use a scrubby pad (the open mesh "sanding" pads - 3m or the red scortchbrite seem to work pretty well).
7. Vinegar solution or evaporust dip works reasonably well to passivate - slightly more professional (and perhaps better results although I haven't tried them) would be some of the metal prep compounds like: Ospho, Metal Ready, or Metal Prep (should be available at the paint store)
8. Plastic tub would be perfect. I think you might want more material than a couple pieces of rebar provide or it'll be pretty slow (there is a relationship between the relative surface areas - if the anode/cathode are close to the same size its generally better). Good idea to have multiple sacrificial pieces since you'll get better paths that way.
9. about 1 tablespoon per gallon of water (not rocket science so "about")
10. Not sure on the aluminum. Personally I just use the old reliable salt and vinegar mix (pour on some vinegar, sprinkle with salt and scrub scrub scrub - rinse with water - also works well with copper) but there is likely a better way. For the pitting.. dunno maybe one of the metal fillers.

One more caveat - make sure to avoid putting brass/bronze parts in the solution as it WILL eat them. I don't know if aluminum has the same problem or not but I wouldn't chance it with anything I loved very much.

 

[glenn bradley]

I've used Evap-o-rust instead of electrolysis. Best price I've found per gallon is at Harbor Freight. Slather on with a chip brush a few times at an interval of an hour or so between, let set over night and rinse off. A little syntho pad here and there for built-up grunge.

.

 

[Carol Reed]

Thanks, Glenn. I like choices. I also hauled home a very rusty plane not long ago. Good practice project.

 

[David Agnew]

Here's my two cents....

7. What do you put on the part immediately after cleaning and before painting and/or waxing to keep the thing from rusting again? Preferably a spray on product. I want to have a paint-able surface without having to remove something else later, if possible. I have low coastal fog to deal with.

I don't. Although I don't have coastal fog to deal with, I always plan to paint/polish/etc the part within a few days. Remember, electrolysis will leave a gray coating on the piece that will need to be removed via wire brush/wheel. I take my parts out, dry them EXTREMELY thoroughly, then do the wire cleanup right before paint, which, as mentioned, could be immediately or as late as 2-3 days later. The gray crud on the object protects it from rusting.

Another thing to mention is you need a VERY GOOD electrical connection to the rusted part. Whenever possible, if the object I'm doing has threaded holes, I will put a couple drops of white vinegar into a hole, let it sit 6 hours or so, then drain it out, then chase the threads. The threads should then be perfectly clean. Put a clean, new bolt into the hole and make your electrical connection to the nice clean bolt. It might just be my bad luck, but I have never been able to simply alligator clip the lead to the object and have it work well, no matter how much cleaning and bare metal it looked like I was clipping to.

 

[Ryan Mooney]

One more cheap rust removal option is citric acid - you can get 5lb and 10lb bags (either is something like a lifetime supply - loml also uses it for some of her wool dying adventures) on ebay for dirt cheap ($15 and $25). Last time I used it I added a couple of ounces to a 6 gallon tub and it did a pretty good job on loose parts.

The upside are that its cheap (competitive with electrolosis and a lot cheaper than evaporust) and removes rust pretty well (almost as good as evaporust imho).
The downside is that it doesn't leave a protective coat of any sort so you need to top dress it pretty fast. If you dip afterwards in evaporust it will leave a bit of a protective film on the piece.

There are also some parts that electrolosis cleaned up that neither citric nor evaporust would get. Specitically if there is crud under crud you can't get out (specific example I have is a stuck shaft has dried grease in it and is also rust welded together no easy way to clean that out). This is because the electrolosis would work from the surface of the metal and blow all the crud off.

Following on Davids note - remember that polished metal doesn't really want to rust very much so polishing instead of painting alos an option for some things. For old saw plates I use WD40 as a lube and polish them with a series of wet/dry sand paper up to around 1500-2000 grit (and use a hard backer block so as not to sad away any remaining etch) and then finish with a cloth wrapped around a piece of plywood and some metal polish.

Also if there is a small amount of red flash rust you can convert it into non-reactive black rust by simply putting the piece into boiling water for a few minutes which will also render the piece more resistant to future rust (indeed this is one step in the "rust bluing" process that was historically used to put a protective coat on firearms - they also traditionally used urine to create the flash rust on the polished metal.. amazing what urine was used for back then.. steel bluing, dying - traditional indego was done in a urine base, hide tanning, gunpowder, and even tooth whitening! ).

 

[Rob Keeble]

Like Glenn i liked the evapo rust but its certainly not a cheap option and when stuff is real rusty it seems to get used up pretty quickly. Went through quiet a bit in no time at all on the car project. Dont leave it open it evaporates like water. But its not harsh on the hands i dont even bother with gloves when i use it and it can go down the drain its bio degradable.

 

[Wayne Eikenberry]

Carol,

Here is a picture of the electrolysis tank (30 gallon garbage can) I used to clean tractor parts a few years ago. I used TSP and just kept adding to the water until I got a real good current flow. I used some scrap steel plate for the anode. It had a lot of surface area and was real easy to clean with a putty knife.

After I cleaned the remaining scale off of the parts with a wire wheel, I didn't have a problem with flash rust. Others that used TSP have said the same thing. I found the TSP in the paint section of the local farm and ranch store.

 

[Garry Foster]

I know that some places have outlawed TSP and what you buy in some paint stores that is called TSP is a substitute. I like the process but have always used washing soda, wi;ll have to give TSP a try if I have another project.

You have probably seen some video's of the process but a retired shop teacher has done several video's on electrolysis, the latest being a Vespa scooter restoration..

In this one he is doing the inside of the tank. He has other video's in that past that are better on the general process.
https://www.youtube.com/watch?v=0Kri-pjJcSE&list=UUKLIIdKEpjAnn8E76KP7sQg

Part 2
https://www.youtube.com/watch?v=4JNtBjCBvNE
Also molasses soak works but it is better for someone that is doing this on a continuing basis..


Garry

 

[David Agnew]

Carol,

Here is a picture of the electrolysis tank (30 gallon garbage can) I used to clean tractor parts a few years ago. I used TSP and just kept adding to the water until I got a real good current flow. I used some scrap steel plate for the anode. It had a lot of surface area and was real easy to clean with a putty knife.

How did you measure the current flow? Hold one end of the object out of the solution so you could put a voltmeter lead on it? I've never been able to get a good reading and am interested in a good repeatable method.

 

[Jim DeLaney]

How did you measure the current flow?...I've never been able to get a good reading and am interested in a good repeatable method.

Not Wayne, but...

I use a 12 VDC battery charger for my power supply, and it has an ammeter built into it, so all I have to do is add the Sodium Carbonate (pool chemical) until I get good current flow. Current can also be varied by adjusting the distance between anode (sacrificial iron) and cathode (piece being de-rusted).

 

[Wayne Eikenberry]

What Jim said!

 

[David Agnew]

Ahh, ok. Well, I'm running a battery in my setup, so that won't work for me.

 

[Randal Stevenson]

Lot's of good advice, and citric acid is a cost wise solution for something the size of the tablesaw (what I am assumming she is going to clean up). I've used evaporust for a lot of smaller projects (like planes) and then wash with water (per directions) immediately followed by WD40 (Water displacement 40), to clean off the water and stop flash rust. Then a light coat of oil or wax (very lightly oiled rag). For larger planes, (#7) it was simple green, green scratch pads and elbow grease.

Also a common thing seems to be battery chargers. I have seen a lot of the small ones for sale for around $5-$10 at garage sales. (bought one for this, but never had a large enough thing to use it on).
Ospho (only bought once, and a friend needed it) I thougth was more of a rust converter (red to black) then a rust cleaner?

 

[Carol Reed]

Ahh, ok. Well, I'm running a battery in my setup, so that won't work for me.

So put an amp meter in line....?

 

[Ryan Mooney]

Also a common thing seems to be battery chargers. I have seen a lot of the small ones for sale for around $5-$10 at garage sales. (bought one for this, but never had a large enough thing to use it on).

One side note - some of the "smart" chargers won't work because they actually detect "stuff" about the battery, the older dummer ones don't and happily send juice down the wire as long as there is a path.

Ospho (only bought once, and a friend needed it) I thougth was more of a rust converter (red to black) then a rust cleaner?

Yeah it would be mostly useful post removal as a continued rust preventative if you can't immediately treat it some other way (i.e. you're sending it out to be painted or powder coated or something that can't happen right away and wax/oil would possibly interfere).

 

[David Agnew]

So put an amp meter in line....?

My knowledge of electricity generally stops at "don't lick your fingers and touch that". A bit of Googling says putting the ammeter into the circuit is the right answer. The next time I zap some rust, I'll see if I can make that happen. Thanks!

One side note - some of the "smart" chargers won't work because they actually detect "stuff" about the battery, the older dummer ones don't and happily send juice down the wire as long as there is a path.

I have a cheap Harbor Freight charger, circa 2 years ago, and it's "smart". It was really hard to get the charger to start sending juice, then it would power itself down after 30 minutes or so; it was very frustrating. So I've got a $35 lawn tractor battery in the loop. The charger will happily send juice down the wire as fast as I drain it out of the battery.

 

[Carol Reed]

So I've got a $35 lawn tractor battery in the loop. The charger will happily send juice down the wire as fast as I drain it out of the battery.

Now that is interesting. If the battery is feeding a load, i.e., the rust removal solution process, the charger sees nothing 'wrong' with the battery. But it sees a load without the battery and that's a problem and it shuts down? So, is the work around for smart battery chargers? I know the older ones are a problem to find. I know turners who use them to fire wood burners. In fact, Don Baer gave me one for that purpose some years ago. Gees, Don, time flies. That charger is, of course, packed I don't where at the moment.

 

[Ryan Mooney]

So, is the work around for smart battery chargers? I know the older ones are a problem to find.

For the vast majority (I'd say all, but as soon as I did luck would have it there's one that doesn't work this way for some reason beyond my ken) you can just put a battery in the circuit (effectively charging the battery with the charger and doing the electrolosis from the battery).

According to this: http://workshopcompanion.com/Demos/...Rust_Removal_Classroom_files/Electrolysis.pdf

"Connect the battery charger to the battery, but don’t plug in the charger yet. Connect the negative (-) post of the battery directly to the tool and the positive (+) post to the part of the iron/rebar/anode that protrudes above the liquid Finally, plug in the charger and turn it on. Should the anode and cathode accidentally touch, the battery or the charger will short out. To prevent this damage, it’s a good idea to add a fuse between the positive post and the anode. The fuse should have about twice the amperage rating as the charger/"

Another pretty good overview with lots of nice tips is here: http://www.rickswoodshopcreations.com/miscellaneous/rust_removal.htm
(although it doesn't address the charger issue)