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I added this to the original post for completeness.
"EDIT: I forgot yo mention on the original version that when installing the heater you should not rely on the screw and butterfly wings to draw on the heater. It should be seated all the way in first. Then, be careful of not over tightening the screw. The instructions say that the torque to apply is 17 to 19 IN-lbs. You can easily feel when the butterfly wings stop expanding. Even with a grip on the head on my small ratchet wrench, I think I could have easily over tightened it."
So to protect my new and expensive all aluminum radiator I installed a "Rad Cap." It has a sacrificial magnesium anode that hangs from the center of the cap. Well the cap started leaking. Grr.
I had the cap that came with the radiator and was it worked but I was worried about the electrolysis.
I found some reference material online about how to determine if electrolysis might be a problem by measuring the voltage between the coolant and the negative post of the battery under various conditions; engine off, engine on, various accessories and lights on and off. I found that I was very likely just fine but I still did not want to run without an anode.
My solution was to create a brass ring that would go into the opening for the radiator cap and from which the anode would hang. I got the idea from a picture at a Corvette forum.
I have yet to go for a drive to check that it still seals.
Below are pictures.
Closeup of the ring. It was made out of 0.016" brass sheet.
The anode from the Rad Cap attached to the ring.
The ring in the opening for the radiator cap.
Last edited by christine_208; 12-22-2019 at 03:48 PM.
what does the anode do? Why do you want electrolysis inside the radiator? originally I was inspired to someday copy you and put an all-aluminum rad in my bravada but now I wonder if it's all over my head LOL?
what does the anode do? Why do you want electrolysis inside the radiator? originally I was inspired to someday copy you and put an all-aluminum rad in my bravada but now I wonder if it's all over my head LOL?
Ah yes. The anode consists of a metal, in this case magnesium, that when electrically connected to the aluminum radiator and also in contact with the water solution, will dissolve ( corrode) preferentially relative to the aluminum.
The science is based on electrolysis that will happen when two different metals are in contact with water. Because different metals have a different level of susceptibility to dissolving, with two different metals one of them will be more likely to dissolve than the other. By introducing a metal even more susceptible to being dissolved like magnesium, the others will be protected.
But for my situation, I also checked the voltage difference between the coolant and the negative terminal of the battery. The amount of voltage drives the chemical reactions. In my case the voltages were small so that the sacrificial anode is more of an insurance policy.
The new radiator came with a screw in anode but I lost it when I had it modified to include the in-radiator engine oil cooler.
so why is electricity introduced to the radiator? do we ground stuff out on the radiator? Or does the electricity spontaneously happen when you have both Metals in the antifreeze? forgive me I've never heard of electrolysis happening inside of a radiator.
so why is electricity introduced to the radiator? do we ground stuff out on the radiator? Or does the electricity spontaneously happen when you have both Metals in the antifreeze? forgive me I've never heard of electrolysis happening inside of a radiator.
No worries. It is a basic chemistry thing. Anytime you have two different metals connected electrically/mechanically and also in a water-based solution, there can be a conduction of electrons and ions in the liquid from one metal to the other. The metal that looses the electrons (the anode) oxidizes (corrodes) and dissolves. The other metal, can gain metal (the cathode) if there are ions of that metal dissolved in the solution. The ions combine with the electrons to deposit more metal on the cathode.
Because no two metals have the same propensity to be dissolved, as measured by a voltage difference relative to a standard (I think silver?), any two metals in contact with the same solution will have one of them dissolve.
Then if there is also a small voltage imposed, it can accelerate this process.
The remedy is to introduce another metal that has a greater propensity to dissolve than all of the others in the system. Magnesium is often used.
If you are familiar with boat, you likely are familiar with the zinc sacrificial anodes that are attached the the out-drives, propeller shafts, rudders or outboard motors so that the anode dissolves in the water instead of the metal of the boat.
Below the effect of two different metals in contact are shown. The relative propensity of these metals to dissolve (the anodic index in volts) are the following: Zn (zinc) = 1.25 V, Fe (iron) = 0.85 V, Cu (copper) = 0.35 V. The larger valued metal will dissolve preferentially relative to the lower valued metal. (Mg (magnesium) = 1.75 V)
@Christine - You are one smart cookie - Well done and as usual well explained!
Just a final clarification of the "circuit" - The engine block is connected to the frame of the car. The radiator is also connect to the frame of the car. The radiator is connected to the block by rubber hoses so there is no "circuit" to the block except via the coolant. So any dissimilar metals will act like a battery. In the case of aluminum and steel a very small current flows. Because the aluminum is the "weaker" metal the electrical process erodes the weaker material.
By putting an even weaker material in the game (magnesium) the magnesium will be the sacrificial metal.
It reminds me of, "I don't have to run faster than a bear. I just have to run faster than you..." - LOL... (Poor slow magnesium...)
11-04-2019, 09:33 AM
