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Old June 14, 2011, 06:43 AM
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Default Dissimilar Metals, Galvanic Corrosion

I know Copper and Aluminium are bad together, now people are saying coper and silver with nickel is bad? I don't have anything that's really nickel plated except for maybe the barbs but would rather just run distilled and a coil so might take my chances there.

But from what I know copper and brass should be ok together right? I want to make a fillport mod for my bayres but it has a 1/2" top so need a reducer, hardware store only has brass. Before I give it a go thought I would ask those that probably would know better.

Also is there a easy way to clean plasticizer off the tubing? rinsing it doesn't help much and don't want to spend forever cleaning, already took forever to clean the block out. Green gritty stuff didn't look like algae didn't look like corrosion, couldn't even think where corrosion would come from with just distilled and a all copper setup (with the exception of the barbs and the coil)

Thanks
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Old June 14, 2011, 07:26 AM
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Copper and brass should be fine, brass is an alloy of copper and zinc, so you shouldn't run into any issues. I don't know about the plasticizer though, sorry.
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Old June 14, 2011, 11:28 AM
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Originally Posted by Corellon View Post
I know Copper and Aluminium are bad together, now people are saying coper and silver with nickel is bad? I don't have anything that's really nickel plated except for maybe the barbs but would rather just run distilled and a coil so might take my chances there.

But from what I know copper and brass should be ok together right? I want to make a fillport mod for my bayres but it has a 1/2" top so need a reducer, hardware store only has brass. Before I give it a go thought I would ask those that probably would know better.

Also is there a easy way to clean plasticizer off the tubing? rinsing it doesn't help much and don't want to spend forever cleaning, already took forever to clean the block out. Green gritty stuff didn't look like algae didn't look like corrosion, couldn't even think where corrosion would come from with just distilled and a all copper setup (with the exception of the barbs and the coil)

Thanks
Don't drink the EK koolaid. It's never been a problem in the past, it only is now because of the quality issues going on.
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Old June 14, 2011, 05:11 PM
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Not exactly a science lesson, but just some basic info in simple terms. There are many factors which affect corrosion, including temperature, ph, salinity of fluid, etc etc...

However, if you are just talking about galvanic corrosion, it comes down the electrode potential difference between the dissimilar metals. The higher the potential difference, the faster the corrosion process will happen. IE the difference between Copper and Aluminum is 2.01v while the difference between Copper and Nickle is 0.59v. Copper and Brass would be slightly worse than Cu/Ni with a potential difference of 0.69v. In any case the "more anodic" material will be "eaten" while the "more cathodic" metal will be effectively protected from corrosion by the anode. In both scenarios the copper is the Cathode, so it will remain untouched while the AL or Ni will be corroded. So from looking at the pictures of other EK blocks and from looking at my own it is very apparent that this is simply an issue with he quality of the plating, rather than an issue of galvanic corrosion.

It is very common to use Aluminum, zinc, and magnesium as sacrificial anodes in water heaters, boats, and even some cars and trains. This is because they have a fairly low potential difference so they will be the anode in most galvanic reactions.

But wait! "Aluminum doesn't rust" many people will say. Forgive me if you already know this, but many people don't realize that Aluminum oxidizes almost immediately in air. The outer layer of the aluminum will "rust" into Aluminum oxide which then protects the underlying aluminum from the air. you can see this if you have a piece of aluminum that is somewhat dull and you scratch it, revealing the shiny aluminum underneath. That dull layer is the Aluminum oxide.

The other thing to consider in a WC loop is that if your fluid is completely non conductive, you will not have any corrosion (assuming there is no indirect contact via the case or wiring). It's pretty impossible to get completely pure water, but the less saline and the fewer minerals in your water the better.

Oh, and I'm not sure what your "green stuff" is without pics, but when copper oxidizes it does turn green. Just look at the statue of liberty or the roofs of the Canadian parliament buildings. However, you really shouldn't have any oxidation in your loop, unless you somehow have a lot of oxygen in your fluid.


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Old June 14, 2011, 05:36 PM
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Most of that is true, however; that first galvanic scale has copper @ +, but to what I dont know. It really has to be referenced to whatever they are submerged in. Copper and Aluminum dont have a potential difference of 2volts. And Copper and Nickel are so close that galvanic corrosion would be so gradual it wouldnt even matter.


I posted pretty much the same thing on another forum dunstin1706...and i got flamed out the @ss lol. Saying that they needed to be in direct metallic contact for galvanic corrosion to occur, was apparently wrong I guess my education in Corrosion is worthless

Good to see someone knows whats what!
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Old June 14, 2011, 05:53 PM
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Originally Posted by MattC View Post
Most of that is true, however; that first galvanic scale has copper @ +, but to what I dont know. It really has to be referenced to whatever they are submerged in. Copper and Aluminum dont have a potential difference of 2volts. And Copper and Nickel are so close that galvanic corrosion would be so gradual it wouldnt even matter.


I posted pretty much the same thing on another forum dunstin1706...and i got flamed out the @ss lol. Saying that they needed to be in direct metallic contact for galvanic corrosion to occur, was apparently wrong I guess my education in Corrosion is worthless

Good to see someone knows whats what!
Yeah, that's why I posted 2 charts, it really depends on the specific alloy of the metal. An "Aluminum" radiator won't actually be just pure Aluminum. IE:, some stronger Al alloys actually contain some copper, so they are much less corrosion resistant than pure Al.

You are right about the contact for sure. Any galvanic reaction needs:
2 or more dissimilar metals
Electrical contact between the metals (can be via a common ground or similar)
An electrolyte

A radiator is definably grounded to the case, but I've never checked to see if a waterblock has continuity to the case or any grounds. Maybe it's a completely moot point?

Galvanic corrosion is a big issue in the oilfield since we deal with tons of metal pipes and vessels and very saline water. Most oilfield stuff use an "impressed current cathodic protection" system though as a sacrificial anode just wouldn't do the trick.
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Old June 17, 2011, 06:19 PM
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Thanks for all the great info, so brass is ok enough I guess but wasn't able to get it all together because of routing in the case, next teardown have to put a T in and fill that way.

Wish I had some pics to show the gunk but didn't have a camera available, can't find anything that really shows any sign of corrosion on it thought, block is fine and barbs are fine, res is acrylic so it's fine unless it's the rad but that's supposed to fine too (Swiftech MCR320) I'll keep a eye on it see if it builds up again but it shouldn't really. Unless the rad has brass in it and the silver kill coil is reacting? Is that much of a difference enough to cause that much corrosion?

Thanks
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Old July 3, 2011, 03:55 PM
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Originally Posted by dustin1706 View Post
A radiator is definably grounded to the case, but I've never checked to see if a waterblock has continuity to the case or any grounds. Maybe it's a completely moot point?
The water-block would be grounded once there is coolant in the loop. The coolant would be the conductive source.

A decade back when much of the WCing community was mostly DIY handmade components other than the pump, the coolants were a mixture of glycol with inhibitors and distilled water with mixed metal components.

Today's cooling loops are so retail based components that the DIY loops are a thing of the past.
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Old July 3, 2011, 06:57 PM
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Quote:
Originally Posted by BMaverick View Post
The water-block would be grounded once there is coolant in the loop. The coolant would be the conductive source.

A decade back when much of the WCing community was mostly DIY handmade components other than the pump, the coolants were a mixture of glycol with inhibitors and distilled water with mixed metal components.

Today's cooling loops are so retail based components that the DIY loops are a thing of the past.

He was referring to grounding via electron flow. You wouldnt have electron flow in the electrolyte.
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Old July 4, 2011, 02:05 AM
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Originally Posted by MattC View Post
He was referring to grounding via electron flow. You wouldnt have electron flow in the electrolyte.

Non-metallic liquid or solid substance which (when melted or dissolved in water or a solvent) disassociates into ions and can transmit electric current through positively and negatively charged ions (as opposed to electrons in metals). Common electrolytes include salts such as aluminum sulfate, ammonium chloride, copper sulfate, sodium chloride (table salt), and acids such as hydrochloric and sulfuric. See also electrolysis.
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