Hello,
I'm looking to solve a problem I have with aluminum. More to the
point, I have a chevy pickup that is eating heater cores every 6
months. I have read where electric current passing in the
antifreeze/coolant is what causes this damage to the heater core.

nakins@sbcglobal.net (noel) wrote in message
news:<ed7c98dc.0401052054.68738c92@posting.google.com>...

I'm looking to solve a problem I have with aluminum. More to the
point, I have a chevy pickup that is eating heater cores every 6
months. I have read where electric current passing in the
antifreeze/coolant is what causes this damage to the heater core.

Just out of curiosity, what does your local Chevy dealer say
about this problem?
Richard

Richard's right. There were similar Alu corrosion problems in

Hello,
I'm looking to solve a problem I have with aluminum. More to the
point, I have a chevy pickup that is eating heater cores every 6
months. I have read where electric current passing in the
antifreeze/coolant is what causes this damage to the heater core. This
current is present, accord to one person, by a bad ground on the
engine. I'm not sure if the heater core itself is mounted to metal, or
comes in contact with any other metal. I'm assuming for now that the
heater core is in contact with metal. I assume that the poor ground is
causing the current to seek a better path. And, the the aluminum
heater core is suppling a connecting point for the current to travel
through.
My question is; If current is present in the antifreeze/coolant,
does the aluminum have to provide a pathway to complete a circuit in
order for electrolysis to occur. If the alumimun were to be
isolated/insulated from making an electrical connection, would this
stop th electrolysis? Or does one need to stop the current from being
present in the antifreeze/coolant?

What seems more logical to me is that the heater core may be acting as
a sacrificial metal: i.e., it is coupled electrolytically to a less
active metal (such as iron) and serves as the cathode in the battery
(more properly, "cell") that results. In a cell of this type,
oxidation occurs at the cathode and the aluminum corrodes away as a
result. A similar situation can result with house plumbing, if
connecting copper to iron pipe. In this case the iron is the more
active metal and will become sacrificial if precautions are not taken.
The solution is to use a "dielectric junction" which isolates the two
metals. There may be a similar fix for your problem.

By definition, the ANODE is where OXIDATION takes place. In all likelihood,
bare aluminum will be an anode and get oxided. It is only if the anodized
aluminum becomes sealed off from the electrolyte that oxidation will stop.

Well, I'm still looking for an answer. I stopped at the dealership and
got a new core. He (Parts Mgr.) didn't know of any solutions but
thought it was odd. The first time he had heard of it. I used to work
with him several years ago. I take him at his word.
I looked the mounting over today and couldn't see any place where it
is making a electrical connection with the body of the truck. It is
held in place by a clip which is screwed to plastic. The only place
where it might make a connection it where the tubes go through the
firewall, but it has a rubber grommet there, so I doubt that the core
is electrically connected to the rest of the truck.
I have read where a ground wire is run to the engine block from the
core. This doesn't seem right to me. It worked fine for 10 years
without it, why now?
Really though, is the core is isolated electrically from the rest of
the truck, and current is present in the coolant, how is electrolysis
taking place?
Thanks

in article ed7c98dc.0401072039.150af147@posting.google.com, noel at
nakins@sbcglobal.net wrote on 1/7/04 8:39 PM:
Well, I'm still looking for an answer. I stopped at the dealership and
got a new core. He (Parts Mgr.) didn't know of any solutions but
thought it was odd. The first time he had heard of it.
I couldn't see any electrical connection with the body
Really though, is the core is isolated electrically from the rest of
the truck, and current is present in the coolant, how is electrolysis
taking place?

You might try connecting a voltmeter between the core and ground. If the
aluminum is an anode in a cell, it will be positive. If the voltage reads
zero, then test for resistance to ground. I don't think that scratching the
outside of the core, especially where there is some extra thickness, with a
test probe will cause a problem. The scratch by being outside of electrolyte
(coolant) should oxidize just from atmospheric oxygen.
Bill

[hanson]