Let's challenge prevailing wisdom

[hmale]

Allow me to philosophize a bit. After reading pH's excellent article on the 5 myths about cooling... I thought it would be beneficial to challenge some of the prevailing wisdom concerning water cooling.

Some of the practices that we engage in are founded in science and practical application...obviously other practices are not. I would like to start the ball rolling with a comment then a direct question to our resident chemist, pH.

My understanding of the commonly used additives in our coolant mixtures e.g. Water Watter, Purple Ice et al, is that they are surfactants, and as such do impact the performance of water cooled systems in a positive manner...to some degree. However, I have found (in my limited reading on the subject) no evidence to support some of the properties that have been attributed to these products. The ability to act as a biocide is one example.

So pH...can you elaborate on what sufactants can and can not do. Additionally, do you have any performance metrics on the relative impact of these substances in a water cooling environment?

BTW, I invite others to challenge and ask questions along these lines.

Cheers!!

[bigben2k]

Good one.

My issue with the additives is this:
Since there are 3 types of corrosion, which ones do they prevent, and to which extent?

1-Acid corrosion
2-Oxidization
3-Galvanic corrosion

[gmat]

Well, i am not a chemist but i have 3 remarks:
- aint 'oxydisation' = 'oxydo-reduction' = 'galvanic corrosion' ?
- if you read all the warnings on a bottle of WW, you'll see this thing is quite poisonous. It contains alkaline by-products, which are (if my memories are right) amongst the strongest poisons around. So i wouldn't see a (terrestrial...) life form developing in such a mixture.
- most people using WW report a 'blackish' colouring of copper surfaces. No doubt it's copper oxyde...

(side note: oxyde comes from oxygen, hence the 'y'. It's true in French but i'm not really sure about it's English counterpart... So, in English, 'Oxide' or 'Oxyde' ?)

[myv65]

Actually, galvanic corrosion is what most folks call the "battery effect" and is due to differing electron configurations of the metals. When you have a conductive path between dissimilar metals, you have an electron potential that basically sets up an electrical circuit. This is most definitely not the same as we English speakers call oxidation.

[nuclear]

wouldn't oxidation (or whatever way you spell it) be like silver that tarnish ?
also, wouldn't putting a little flow of electron in the opposite way (like trying to charge a battery) eliminate the effect of galvanic corrosion ?

[myv65]

Oxidation may or may not be beneficial. Stainless steels, for example, rely on oxidation to protect themselves. Chromium oxide forms literally within thousandths of a second upon cutting stainless steel. It is this oxide that resists further corrosion in stainless steels.

Some weathering steels use copper as an alloying agent to form a protective layer of oxide. You used to see this in light posts, etc. Not sure how much it's used anymore.

Imposing an electrical charge to fight galvanic corrosion isn't easy. The voltages and currents are neither completely steady nor very large. Use lots of electricity and you have yourself an electro-plating operation, albeit not a very efficient one. In some cases you'll find "sacrificial" metals used to reduce galvanic corrosion. It's been many years since my material science class that talked about all this, so I'm a little "rusty" on the details.

[bigben2k]

Thanks myv65, that's a lot of good info.

Oxidization is definitely not the same as galvanic corrosion.

What hasn't been covered yet is acid corrosion: the attack on metals from H+ or OH- ions (the components of H2O). with Copper, which forms a Cu (+2) ion, the OH- attacks it, or pulls the copper atoms from the copper block.

Keeping a solution neutral would seem to be the way to go, off-hand, but on the other hand, I wonder what would happen if the solution was more acidic (lower than 7 pH) versus more of a base (higher than 7 pH level). pH? (oops, I mean pHaestus?)

[jtroutma]

BigBen,

Going more acidic does not sound productive to me. Acids usually attack (or react) to both organic and metalic elements becuase of their very nature.

My chemistry skills are very rusty but from what I think I remember:

Acids are chemicals that are negatively charged particles that want to become neutral. When they come in contact with both organic and metalic compounds, they break apart other compounds around them to create electrically neutral compounds. This reaction "tears" apart the original compound and thus is the reason why you see all that "bubbling" when you pour an acid onto something.

A base usually only attacks (or reacts) with organic compounds. However after a very interesting experience last night with some EXTREMELY HIGH concentrations of Sodium Hydroxide solutions, even a base will react with metailic compounds. (In short, it started eating through the aluminum can I was using to mix the stuff in )

Personally, I would think it would be better for a watercooled system to be slightly basic, not acidic. Acidic enviroments usually led to the "battery affect" and thus should be avoided like the plaque.

Again I could be completly wrong but at least I try and expand my knowledge base.

[pHaestus]

Corrosion vs. oxidation:
Oxidation is the loss of an electron (this is always coupled with another substances gain of electrons since electroneutrality must be maintained). So Cu--> Cu2+ +2e- is an oxidation of elemental copper to copper ion.

Corrosion: Closely related (in natural systems) to oxidation, the reaction of a metal ion with (usually) water to form hydroxides and oxides.

Cu 2+ + 2H2O --> Cu(OH)2 + 2H+

Rust is a ubiquitous corrosion product.

Strictly speaking, galvanic corrosion is when metals with different redox potentials come in contact with one another in an electrically conductive medium (water). Here is a good explanation from my alma mater:

http://www.ocean.udel.edu/mas/masnotes/corrosion.html

Regarding the chemicals in water wetter:

Bacteria and fungi typically grow in slightly to moderately acidic conditions. Water wetter is basic and so the pH of the water is not as hospitable to microbes. Surfactants may or may not participate in the reduction of microorganisms; not my field. I would tend to think of them as a carbon source and therefore potentially another food source for microbes.

[Bignuts]

The reason that surfactants may be beneficial in the automotive cooling arena is because that they help reduce the localize boiling that may occur in a typical engine, especially the cylinder heads.

The benefits can vary wildly in production engines, because the manufacturing process can leave things like flashing and casting inconsistantcies that can cause more localized boiling in one engine over another engine, even though both came off the same assembly line.

What you have to ask yourself is if you believe that your system reaches the temperatures to cause boiling in the waterblock (I hope yours does not!).

On the other hand, using water wetter to combat system corrosion is a diffferent story, but Redline offers no guidelines as to the change interval (if there is one), so I am unsure of how long it will offer protection.

One thing is for sure, if you can use water wetter instead of antifreeze for corrosion protection, you will be more efficient in moving the heat loads to the radiator, due to the lower concentration of wetter needed compared to the amount of antifreeze.

[bigben2k]

Before we go on...

I have to put up a link to another thread here, where DigitalChaos compares Redline Water Wetter and Purple Ice. .

There's 8 pages, but throughout all of it, you'll see a pattern, and some solid info.

But it's not the complete info we're looking for.

The question comes down to how many different metals you have in your rig.

1- Copper and aluminium
2- Copper and brass (yes, those barbs)
3- all copper, or all aluminium

I'll have to re-read the whole thing again, to summarize it all, but the options are:

a- Distilled water only
b- 2 oz of Redline Water Wetter per gallon
c- 4 oz of Redline Water Wetter per gallon