so how do i stop batery effect

so yeah alum block , copper rad ?????

Use regular ol' anti-freeze. Someone here should be able to tell you the right mix.

just enough antifreeze to tint the water slightly green,
about 5%
or use waterwetter

Dunno if anyone has tried this, but you can retain the electrolyte status of the liquid and hence the thermal conductivity of it by just keeping it 100% good ol tap water, as long as you provide a reducing agent to be oxidized instead of the aluminum. A piece of lithium affixed to your waterblock would probably do the job - this is the same technique used on boats. Of course you would still have to deal with all the bio's in the water... alcohol or something for that though.

arhines said:

A piece of lithium affixed to your waterblock would probably do the job - this is the same technique used on boats.

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Do you mean on the inside or outside of the waterblock? And how does this work?

Just curious.

It could theoretically be placed anywhere on the piece of metal which would normally be oxidized. Hm, i would have to go into chemistry with electron transfer, galvanic cells etc (thats how it gets "battery effect" nomenclature), but the basic idea is this:
You can create a list of elements in order from "easiest to react with" to "hardest to react with". Now, rusting, the process of oxidation is really just the transfer of electrons/protons (what do they call it these days? I think electron pair transfer is called bronsted-lowry model, and proton is the more general term...but its a bit fuzzy) from one element to another. In this case, I believe it is from the copper to the aluminum, but it could be vice versa. Similar to the list of easiest to hardest to react, you can create a list of which elements are most easily oxidized, and which are most easily reduced (oxidation is gaining electrons, reduction is loss of electrons (o.i.l.r.i.g...the one thing i remember lol)). If the two elements are at opposite ends of the spectrum, they will very easily create a redox reaction - which is what is happening to the copper and aluminum. The copper is reduced, while the aluminum is oxidized (or vice versa...ill think about that later). Now, if you throw in something else, which is even further at the end of the spectrum, the situation changes. Say the list is 20 elements long, 1 being easily oxidized, 20 being easily reduced. Say aluminum is near the top, at position 3, while copper is near the bottom. Lithium, however, is number 1, so copper would "rather" get electrons from lithium than from aluminum, because there is a greater difference between the two (i believe the difference in this case is measured by electronegativity). So, the bottom line is that copper reacts with the lithium instead of the aluminum, regardless of what is in between it - as long as it has an electrical connection (in this case, through the water), it will do this.

Actually, adding anti-freeze will add to the battery effect after a while. After a certain amount of time, it becomes slightly acidic, thereby adding to the effect. Using watter wetter or purple ice should help extend the amount of time before the mixture becomes acidic. A good way to check if it's become acidic is to used a voltmeter, set to measure DC voltage. Put one probe in your coolant, and touch the other on a metal part of your rad/heatercore. You'll probably some sort of voltage no matter what. It's normal when you have any kind of setup like a water cooling rig. Even if you use all the same material (all copper, all aluminum, etc...). If the mixture reads more than 0.20V - 0.25, it's probably time to flush the system and put in fresh coolant.

arhines said:

....So, the bottom line is that copper reacts with the lithium instead of the aluminum, regardless of what is in between it - as long as it has an electrical connection (in this case, through the water), it will do this.

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Thanks, arhines! Fascinating stuff. I am seriously considering giving this a try. A couple questions though. Where can I get the kind of lithium I would need to do this, and, would I have to replace it every so often? I think I will use CrystaMethods idea of using a voltmeter to see if this works.