Battery Effect In waterblocks Need A Suuggestion

[Titan]

I need an advice....i reall really want to mix copper and aluminum together to make a waterblock. And i know the effects of it but i was wondering if anodising the waterblock would be of any help....

[joemac]

Yes it would help make sure you use at least type 2 anodizing. This is what I have been doing with my blocks and I haven’t had any problems with the battery effect.

[Since87]

Hint:

Study the design of any modern Swiftech block. Their solution is better than just anodization.

[murray13]

Oh you mean things like nylon barbs, gasket matl. between Cu and Al, fully annodized even threads, things like that???

[Since87]

Yep, those were the things I was thinking of, but then you mentioned threads, and that reminded me that there is most likely an electrical connection between the baseplate and the top through the screws.

Plastic shoulder washers there could make the Swiftech blocks vastly less susceptible to galvanic corrosion than most other blocks with aluminum tops.

[joemac]

Originally quoted by Since87
Yep, those were the things I was thinking of, but then you mentioned threads, and that reminded me that there is most likely an electrical connection between the baseplate and the top through the screws.

That is hitting the nail on the head. The battery effect is reliant on different metals paired in some type of conductive solution. In the water blocks we a discussing these two different metal are aluminum and copper. In this type of environment the aluminum will start releasing ions into the water; adding de-ionized water will not help. The water will no longer be de-ionized once the aluminum begins releasing ions. The galvanic action will corrode the aluminum faster than the copper. To make a very long explanation short, Shorting the two metal on a small scale like this tends to slow down the battery effect add anodizing on top of this and the process is further retarded. Run a wire from your block to the radiator and the whole system is an electrical short. I think someone else in the forum came to the same conclusion I did by means of theory and testing (#Rotor I think).

[Titan]

Thanks guys... now i know where i will be heading. Guess i will be anodising the aluminium by 2 microns. but short circuiting the 2 metals together would be a little problematic as i have no "SAFE" power source to do it. Still swiftech does a fine job for their aluminium tops is there a site which uncovers the mystery of the coating on top of swiftech blocks....i may want to read it up

[Teus]

I'm using copper blocks and an aluminium radiator. I've bought antifreeze designed for car cooling systems, on the bottle there's written it prevents corrosion and those calcium residus from water. I'm using ~10% antifreeze, is that good enough?

[joemac]

Titan

Thanks guys... now i know where i will be heading. Guess i will be anodising the aluminium by 2 microns. but short circuiting the 2 metals together would be a little problematic as i have no "SAFE" power source to do it.

You don’t need a power source to do it. Just make sure your screws provide an electrical connection between the two metals. Then make sure there is an electrical connection between your block and your rad.

[Titan]

Originally posted by joemac
You don’t need a power source to do it. Just make sure your screws provide an electrical connection between the two metals. Then make sure there is an electrical connection between your block and your rad.

OIC now i get what u are saying. I have something new today. Thanks for the advice.

[redleader]

Run a wire from your block to the radiator and the whole system is an electrical short. I think someone else in the forum came to the same conclusion I did by means of theory and testing (#Rotor I think).

Thats not going to help you at all.

Even if that idea was reasonable, I'm curious how increasing the current through your system is going to help things? Unless you often short batteries to help them keep their charge

[Alchemy]

Putting two dissimilar metals in physical contact makes it likely for corrosion to occur at the boundary between them, which is quite bad. Of course, concentration cells can form along seams of a single metal, so it's generally best to design blocks with rubber seals and nylon screws, though it's difficult to say how much benefit can be seen over the relatively short lifetime of a waterblock.

The voltage potential between copper and aluminum is not altered by reducing the resistance of the electrical contact between them, which is what "shorting" them does.

However, the current between them can certainly be increased by wiring them together. I=V/R. More current means more electrons moving, which means more oxidation.

Of course, there's such a low concentration of metal ions in the cooling fluid that it's possible it won't make a bit of difference.

Alchemy

[Althornin]

Originally posted by joemac
That is hitting the nail on the head. The battery effect is reliant on different metals paired in some type of conductive solution. In the water blocks we a discussing these two different metal are aluminum and copper. In this type of environment the aluminum will start releasing ions into the water; adding de-ionized water will not help. The water will no longer be de-ionized once the aluminum begins releasing ions. The galvanic action will corrode the aluminum faster than the copper. To make a very long explanation short, Shorting the two metal on a small scale like this tends to slow down the battery effect add anodizing on top of this and the process is further retarded. Run a wire from your block to the radiator and the whole system is an electrical short. I think someone else in the forum came to the same conclusion I did by means of theory and testing (#Rotor I think).

galvanic corrosion, as Alchemy says, will not be prevented by "Shorting" them.
It could be prevented by applying an exact opposite voltage to them, however.

[Since87]

Originally posted by Althornin
galvanic corrosion, as Alchemy says, will not be prevented by "Shorting" them.
It could be prevented by applying an exact opposite voltage to them, however.

Exact opposite voltage?

The attached picture shows one battery connected with "opposite" polarity to another battery. This is still a short, but with twice the voltage driving the reaction. Perhaps I'm not understanding...

[bigben2k]

Since87: take one of those batteries, and flip it around: "exact opposite voltage".

It's used in marine applications, to help reduce corrosion on freighters.

[Titan]

After all the lessons u guys taught me i think i found the best way to do this after all. I will seperate this 2 metals using a piece of rubber sheets...

[Titan]

And also strong plastic screws to hold them together(to prevent any ions flowing through them) and distilled water. I think that settles all.....next time i will use 1 metal for my block to save me all this trouble.....

[joemac]

This is what I am saying here … I started to test blocks using dissimilar metals (Aluminum and copper) several years. Knowing about the battery effect I decided that I would do a test to see how long it would take for my test block to show signs of corrosion . Using anodized aluminum, o-ring, metal screws and copper the system ran for 10-months in a setup. Getting tired of not have any action (Yes I can be patient) I took the system apart. What I found was no sign of corrosion. So I came up with a possible theory on why this was happening in this environment. I am not talking about a bridge or a ship in the middle of the ocean; I am talking about a water block used for I.C cooling. Some time later while reading #rotor page (under the FAQ/ the battery effect) I found that someone else had found something familiar . So I am not spitting out my theory on what I think would happen but why something didn’t happen in an experiment.

[Althornin]

Originally posted by Since87
Exact opposite voltage?

The attached picture shows one battery connected with "opposite" polarity to another battery. This is still a short, but with twice the voltage driving the reaction. Perhaps I'm not understanding...

as BB says, you've got it backwards.
The potential created by the mixture of the metals is easily looked up ont he web.
Applying this voltage "opposite" the created voltage will negate any galvanic corrosion, because no effective electron flow will be taking place.

[Since87]

Originally posted by Althornin
as BB says, you've got it backwards.
The potential created by the mixture of the metals is easily looked up ont he web.
Applying this voltage "opposite" the created voltage will negate any galvanic corrosion, because no effective electron flow will be taking place.

Seems like a strange usage of the word "opposite" to me, but I suppose it's just a matter of perspective.

In any case, the added voltage source does no good unless there is a reasonably high resistance leakage path. (The resistance shown as a zig zag line in the attached image.)

If the leakage path is not there, then the added voltage source serves no purpose - there is no current flow to stop.

If there is a leakage path but it is 'high' resistance, then the added voltage source can provide the current to maintain the correct voltage across the resistance, and prevent current from flowing through the Galvanic cell.

If there is a leakage path but it is low resistance, then the amount of power required to stop the flow of current through the Galvanic cell is excessive.

Eliminating the leakage path, seems the most practical solution wrt waterblocks. (Assuming protection beyond chemical corrosion inhibitors is desired.)

[Althornin]

Originally posted by Since87


Eliminating the leakage path, seems the most practical solution wrt waterblocks. (Assuming protection beyond chemical corrosion inhibitors is desired.)

Ok, maybe im not understanding you, but a galvanic cell operates on a simple principle, iirc:
two dissimilar metals in an aqueous solution that forms a salt bridge between them. If the two metals are then connected electrically via another path, then a galvanic cell is formed - assuming the potentials of the metals is far enough apart, etc.

i dont understand your use of "leakage path" - are you refering to the salt bridge that is formed? (metal ions....)
Because if you are, then dont worry - there arent that many metal ions in the water, and so the salt bridge will limit the current transfer.

Best way to prevent galvanic corrosion is to simply electrically isolate the two metals. You could also toss in a zinc anode as a sacrifice. Or, as i stated earlier, you can apply the potential voltage in reverse.

[Since87]

Originally posted by Althornin
i dont understand your use of "leakage path"

By "leakage path" I mean an electrically conductive connection between the two metals. In the case where the two electrodes are in contact, that path is the connection point(s) of the electrodes. Otherwise, something else, like steel screws, or a smear of AS could provide a leakage path.

Originally posted by Althornin
Best way to prevent galvanic corrosion is to simply electrically isolate the two metals... ...Or, as i stated earlier, you can apply the potential voltage in reverse.

But, if the top and bottom of your waterblock are aluminum and copper, and they are bolted together using threads in the aluminum, then the electrical resistance between them is likely to be on the order of 0.001 Ohms or less.

Off the top of my head, I'll say the desired voltage differential between the copper and aluminum is 2V. Maintaining 2V across a 0.001 Ohm requires 2000 Amps. So doing this would require dissipating 4 KW in the joint between the copper and the aluminum. Kind of makes corrosion a moot point.

Electrically isolating the metals is the only 'good' solution. (Coolant chemistry aside.) I don't think I'm saying anything substantially different than you, just pointing out practicality issues.

BTW, aluminum is more electronegative than zinc. You'd need to go to magnesium as your sacrificial anode.

[Sapientiea]

Hi Guys!

I'm new and im reading through the watercooling topics for the first time, when i read this topic. I have a solution for the battery effect. Like has been said before, the two metals will release ions in the water and subsequently the battery effect will occur.

Now if you add a thirth metal (for instance: lead or common iron) the battery effect will occur on the least noble metal, in this case lead or iron!!
You can add a small piece of an other metal in your reservoir! Adding other substances to the water, like anti-fries (sorry dont know if this is the correct english word for it, but people use a substance used for cars to add to the water to neutralise the battery effect), this will lower the waters heat transfere/uptake capacity.
What you can add to the water is anti-foam (in the university in which im working we use this to prevent foaming caused by dying bacteria...) it will lower the surface tension of the water. This will have two main benefits:1-it will increase (optimise) the transfere of heat, and 2-It will have a great effect on the air-bubbles in your WC-system, the bubbles will not stick to the walls of the tubes and they will be smaller and will be carried out more quickly by the water to the reservoir!!!! i cannot remember the name of the substance we use, but i think it is silicone-gel....i'll post the name if i know the name

Ok so far my contibution to this topic, i hope i added some 'new info' and if i didnt.....ahhh well i tried anyway!

Sapientiea

[Teus]

great info

I'm using antifreeze right now, it prevents corrosion and foam. can you give me some more info on that 'third material' theory, and if possibly any results from tests?

I'll look into it, and try to do some testing with distilled water, distilled water w/ antifreeze and that 'third material' stuff

[Since87]

Originally posted by Sapientiea
Hi Guys!

I'm new and im reading through the watercooling topics for the first time, when i read this topic. I have a solution for the battery effect. Like has been said before, the two metals will release ions in the water and subsequently the battery effect will occur.

Now if you add a thirth metal (for instance: lead or common iron) the battery effect will occur on the least noble metal, in this case lead or iron!!

Galvanic corrosion will corrode the most electronegative metal. If you look at this Table of Standard Electrode Potentials you will see that only a few metals have a more negative electrode potential than aluminum, and of those, the only one that is 'practical' to use is magnesium. (I already mentioned this in the post right above yours.)

To be useful, the magnesium needs to be wired to the aluminum, (or otherwise connected with an electrical conductor) and the wire used can't be exposed to the water.