At 10:12 am 6/3/97 -0700, you wrote:
>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
>
Roland,
If you are going to all that trouble, then check out a good marine store.
There is an electronic corresion protection system that uses a regulated
voltage ( or current?) and a platimum electrode. It works fine for
expensive boats; but it raises hell with any boat docked nearby as the
nearby boat has a worse electrolis problem. I have seen a similar
system for cars that is alleged to prevent rusty bodies.
Jim Barrett 351C and others
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