Galvanic corrosion for Silver + Aluminum
 

Does anyone have any experience using silver and aluminum (or aluminium :) ) in the same loop? How about silver and copper? I'm curious as to what happens when use a G5 waterblock with radiators made of other metals.

silver has a bigger redox potential (+0.8V) than copper (+0.34V) so chemical reaction between silver and alu (-1.66V) will be stronger because of the greater difference between potentials ! Alu will destroy faster, use inhibitors !

A very bad idea, stick with silver/copper/brass/plastics and you will be fine. Why mess around at all with aluminum?

What you will see when I finally start selling the G5's is an EXTREMELY strong recommendation from me to avoid any use of aluminium in your loop. Don't even bother trying to control it with corrosion inhibitors. You probably can control it with enough effort, but it's just asking for trouble, and you will probably need to replace the inhibitors fairly regularly, such as every 3-6 months. The silver will eat the aluminium very rapidly, and if the aluminium is anodised, then its anodisation better be perfect, or it will find any weakspot and start eating it even more aggressively than copper does.

I concur.

I recently picked up a used block (for the WBTA collection); a Spiral block from DTek. Not sure if anything was used, but it was heavily corroded.

This thread reminds me of my old days working as a Machinist/Tool & Die maker at CATerpillar
helping design water cooling & radiator test rigs. :)

My opinion is only really makes any difference if the metals are physically touching - dont know why.. but all of my stuff is fine.. Never used corrosion inhibiters, only d/I water + a biocide.

My d4 pump impeller is perfect - apart from the chip of the annodising that was there when it was new..... and I would assume that impellers would be the first thing to go.. if theres no contact of course..

If you have a lot of wetted bare non-annodised aluminuim then maybe avoid.. but I would say annodied is fine.. still wouldnt use it for a block's top and never touching copper/silver though...

Also some alloys of aluminuim (its rarely pure for many resons) have copper and a few others in them.. I wonder if that will eat itself.. jut and interesting not-related thought..

edit: why bother using a silver block if youve only got an alu rad? I think youd get better performance using the same block but both it and the rad in copper, and cheaper aswell?

Physical contact isn't required since the reaction is between dissolved metal anyway.

Adding dissimilar metals to make an alloy increases the resistance of the metal because one element can be sacrificed to protect the other. This is why they add zinc to iron when making steel. They don't eat one another because the reaction is not occuring in the metal, but rather between dissolved ions floating in the water and the surface of the metal.

The D4 impeller and body is made from passivised 304 stainless steel, which is not galvanically reactive with copper or silver. Passivised 304/316 SS sits about mid-way between copper and silver on the galvanic reactivity scale. It is about as reactive with either silver or copper, as brass is with copper.

?
do they really do this? I am curious and not a metallurgist.

Actually maybe not. I just googled it and zinc google says its added to the outside of steel to protect it. I remember reading some something about zinc and steel, but its possible I'm thinking of brass instead.

Yes I am curious too. Zinc is used as a protective coating (galvanizing) far as I know.
Not sure I understand the part about one element being sacrificed to protect
another. The zinc atoms may share a few electrons (ion) but the zinc will still be
present unless you have some sub-atomic fission going on.

The main thing with modern steel production is the use of forced air to help oxidize
the excess carbon & silicon. That is the very essence of the Bessemer process which
changed the world as we know it.

Slightly O.T.

But then again, the topic is morphing a bit, lol.

Steel {mostly iron with a bit of manganese and generally less then 2.5% carbon} screws are often either zinc plated or cadmium plated to prevent the steel from oxidizing in the presence of moisture - and air.

Over time, the plating never holds up, especially when the screws are exposed to the elements.

The fact that the coating is eventually gone - shows it has done its job up until the point of failure as its "job" was to shield the underlying steel from oxidation - and to provide sacrificial cathodic protection as the coating gets eaten away over time.

Galvanizing, generally hot-dipped galvanizing submerges steel in molten zinc and upon cooling, provides a thicker, better bonded coating then . . .

. . . so-called cold galvanizing, applying a coating of powdered metal in suspension - with a brush or spray method.

My experience in this WC arena is limited . . .

I notice that, all of the hardware supplied by Danger Den for their blocks {with the exception of the springs} is either stainless steel or brass.

Another leading manufacturer of WC kits, supplies hardware with plated steel screws.

In the overall scheme of things, the cost differences are trivial, but the folks who include the more application-appropriate hardware send a message that they probably pay more attention to all other relevant details, whether 'tis true or not.

Three of the five "homebrewed" systems I have built thus far were built into Lian-Li aluminum cases. Though arguably unnecessary, I discard my plated hardware when putting the aluminum chassis PCs together {especially a water-cooled PC} and replace all with stainless.

I'd stay away completely from mixing aluminum into the cooling circuits.

Cheers,

Joe

Good Steel Dictionary here