Okay, thanks to another list member I found out that the chemical
table I was referring to in my post on radiators and water chemistry
is called the Electronegativity Table. So I looked into it a bit,
and while I make no claims about fully understanding what reactions
are likely to take place between the metals commonly found in radiators,
I did learn the following:
The atom with the higher electronegativity value will always "pull"
the electrons away from the atom that has the lower electronegativity
value. The degree of "movement or shift" of these electrons towards
the more electronegative atom is dependent on the difference in
electronegativities between the atoms involved.
Here's a list I made from the periodic table of elements:
Element Electronegativity
------- -----------------
F 3.98
Cu 1.9
Fe 1.83
Zn 1.65
Al 1.61
Mg 1.31
I've included Fluorine as a reference because it has the greatest
attraction for electrons. Hopefully you don't have any in your
radiator. Maybe we should be avoiding fluoridated water too? It might
be good for your teeth, but perhaps not so good for your radiator.
As I suspected, zinc is in between aluminum and copper in this table
while magnesium is below aluminum. What would this mean for a radiator
containing all of the metals listed? I dunno. Maybe all of them except
the copper (and iron because of its sheer mass) would be dissolved in
short order. What I would like to do is conduct an experiments. I was
thinking of putting various combinations of these metals in a jar of
salt water and see what happens. Does anyone have suggestions on
sources for small quantities of zinc and magnesium? I can probably find
zinc at a hardware store, but probably not magnesium. Maybe welding
rod, but I'm not so sure this would be commonly available. Anyone with
a chunk VW engine block they don't need?
One factor that I haven't seen mentioned is coolant ph. Exposed
aluminum oxidizes almost instantly, forming a coating that is both a
good insulator and literally tougher than nails. But both acids and
alkalines remove this oxide pretty quickly. Presumably keeping the
coolant's ph near neutral would protect this coating. Maybe that's part
of what coolant corrosion inhibitors do.
Another approach might be to eliminate all copper and brass from the
cooling system, but I think this would be tough to do. What about the
thermostat, heater core, heater cut-off valve and even the water
temperature sensor and fittings?
Using demineralized water is no doubt a good start, but coolant systems
aren't very clean environments. I doubt demineralized water stays that
way long once poured into a radiator. Even if I decide against an
aluminum radiator, I'm still stuck with an aluminum water pump and
intake so I'm gonna go for all the protection I can get- demineralized
water, corrosion inhibitors and a sacrafcial anode, if they work.
Roland
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