Can brass bushings in cast iron be damaged by electrolysis rust removal process ?

I have large casting with a brass sleeve through it that I need to remove without damaging it. It is on a single cylinder crude oil tractor cylinder head and is projected through the cooling water with the rust from the head sealing both ends of the brass so although I have it "loose" it can't be removed without removing the rust build-up from the actual head casting itself ! will the electrolysis process damage the brass sleeve or will it simply conduct the electricity without damage?

Thanks,
Graham

I've not tried electrolysis, but my understanding is it only works "line of sight", meaning there cannot be anything between electrode and object you want to clean, but like I said, I have not tried it. I use evaporust, it works anywhere it can get to, provided there is no oil contamination.

dalmatiangirl61 said:

I've not tried electrolysis, but my understanding is it only works "line of sight"

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Thanks "Dalmatiangirl61" for the reply, and yes, it's my understanding as well !

I have used electrolysis successfully for near on five years now, but I have never had an "unmovable" non ferrous cathode to deal with before. What I need to do "is" line of sight, the brass tube is an injector mounting sleeve that travels through the cooling water and screws into the head casting at its bottom edge meaning it has to be rotated to screw out of the casting and although the tube is loose enough to move, it can't get past the built up corrosion to continue being unscrewed up and out of the head. The head has a left and right hand covers that can be removed to see the tube but you can't actually get at the top section where the corrosion is to physically remove it, hence wanting to try and do it electrically, just needing to make sure it won't hurt the irreplaceable tube by the operation.

I have heard people from the US talk about "eveporust", but have never seen it out here in Australia and have never heard of anyone using it so I think it may not be being imported here (at least in West Aust) I may do a bit of looking to confirm that as it could potentially do the trick.

Graham

No idea what electrolysis may do.

However, if you cannot get evaporust, the other thing that works on rust anywhere is acids. I use phosphoric, as do many others.

I can tell you that you DO NOT want to do an acid treatment with that brass sleeve in there. If it really is brass, the acid will take out the zinc on the surface, and possibly deeper if it has to soak any time. That will not be good for the integrity of the surface.

If it is actually bronze, I am not sure what it may do.

Ah, missed the Stralia location, another member said evapo was not available down there. There is a homebrew evapo, never tried it, supposedly EDTA is main ingredient of evapo, do a search for "EDTA rust removal".

Thanks for the input JST and Dalmationgirl61,

I did some "Googling" after posting my previous reply and found out that "evaporust" "is" available over here, but very expensive. I think I will get some and try it on a smaller project, but if I need to submerge it like they say I would need to buy about thirty gallons to submerge the head assembly, that cost would translate to $600 (Ausy) or about $500 US.

I have been talking to another electrolysis user who said electrolysis didn't seem to damage the yellow metal fittings on one of his projects. I say yellow metal because he didn't know if they were "brass" or "bronze". I suspect his bushings may have been "bronze" where as my sleeve I think is "brass". Anyway I have decided to give it an overnight try and inspect it in the morning to see if any adverse reaction is happening. If anything is happening I think I should see something by then and if nothing seems to be happening I will put it back in the bath.

Thanks for the interest,
Graham

If you want to you can contact this guy, he does a lot of this on all different kind of things. If anyone would know I would talk to him. And he is a lot closer to you than most of us.

Record : A Triple Vice Restoration - YouTube

Charles

Molasses works with the same principles of Evaporust. It is significantly slower (and, of course, prone to bacterial/fungal contaminations which could release acids and other corrosive chemicals), but much cheaper.

Paolo

I think electrolysis is much less likley to damage anything than straight chemical methods.

Chemicals and dissimilar metals will make up their own minds what sort of electrochemical reactions will take place....all corrrosion os electrochemical. The iron may protect the brass. The zinc may be etched out of the brass leaving spongy copper.
If you impose an external voltage, then you will be guaranteeing that everything but your positive electrode is protected, by a voltage high enough to cancel out any self-generated potentials.

Well !
I put the head in my tub overnight and ran the charge through it for about 16 hours before taking it out and "closely" inspecting it to check that it wasn't affecting the brass, and I believe all is going fine ! A lot of the rust shale and build-up is being removed and there doesn't appear to be any reaction on the brass to be seen, so after checking that I still cant remove the sleeve I put it back in the tub for what will be a longer time. (cross fingers all appears fine)

Paolo MD.
I used to use "molasses" exclusively a few years ago, but after trying electrolysis I haven't used it since ! It does work well and I do actually have a five gallon bucket of it here but not used it "yet".

Thanks guys for the input,
Graham

magneticanomaly said:

I think electrolysis is much less likley to damage anything than straight chemical methods.

Chemicals and dissimilar metals will make up their own minds what sort of electrochemical reactions will take place....all corrrosion os electrochemical. The iron may protect the brass. The zinc may be etched out of the brass leaving spongy copper.
If you impose an external voltage, then you will be guaranteeing that everything but your positive electrode is protected, by a voltage high enough to cancel out any self-generated potentials.

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Well, unless you count the hard black "shell" that electrolysis has always produced on the parts I tried it on. That stuff is very hard to remove. Makes the process not even worth bothering with.

I have been told that the "hard shell" is due to a much too high current used. That cannot be the case, as the sources I was using were actually rather weak.

JST,
I have used electrolysis quite successfully in the past and the "black residue" you speak of was not a problem. It was there, but all it needed was a light going over with a wire brush and then a wash in water. The black was there but it came off very easily where as the rust was very hard to shift. Molasses no doubt would have done the job, but I quite like the results I have had with electrolysis up until now. I do use a very small battery charger though (4 amp max) and it cleans up quite large parts well, but it also cuts out if I put the anodes too close to the work. The fact that the small charger needs to have the anodes a distance away from the work to operate well may stop the black build up like you say you experienced. When I set the tank up I move the anodes in (usually one on each side) until the resistance is such that the charger is charging about three amps, and that seems to work fine, if I put the anodes too close to the work there is less resistance and the corresponding higher flow rate will trip out my small charger, if it was able to pass the higher current flow it may very well have made a "hard shell" like you have experienced.

Whether I still like the electrolysis method as much in the future may depend on how it handles my current project, because if I still can't move this brass sleeve in the next couple of days I will probably try it in molasses.


Thanks for posting JST, its always good to hear experiences other have had both positive and negative, I can file those away in the memory for future reference when something goes "pear shaped" (as it at times always will)

Graham

It's not the total current that matters, but the current per cm^2.

The "legend" is that if the current per unit area is too high, the "shell" appears. But no matter what current level I used, I always got the hard shell.

That "shell" was actually much harder to remove than the rust. I definitely would rather wire brush the rust than wire brush the "shell" off the part, so I decided to "eliminate the middleman" (the electrolysis).

Actually, I just use phosphoric acid, or for more "appearance" parts, I use "Evaporust". Phosphoric will work in 45 minutes or less, and you want to remove the part by then to avoid it darkening a bit. Evaporust varies, but it does not matter if you leave the part in longer.

BalkaRoo said:

Thanks for the input JST and Dalmationgirl61,

I did some "Googling" after posting my previous reply and found out that "evaporust" "is" available over here, but very expensive. I think I will get some and try it on a smaller project, but if I need to submerge it like they say I would need to buy about thirty gallons to submerge the head assembly, that cost would translate to $600 (Ausy) or about $500 US.

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No need to use a huge amount of Evaporust. You can make a wooden box or a sand impression and line it with a plastic bag so you don't need so much. You can also lay on paper towels soaked in the stuff and cover with plastic wrap to keep it wet.