Re: Non-Phosphate

[Robert Myers <rmyers@wvit.wvnet.edu>]

Bob,

There may be something in your comment about a "marketing thing".  However,
there is sound chemistry behind it.  Aluminum phosphate has all the
solubility properties of a chunk of granite.  The presence of phosphate in
your coolant will force the concentration of aluminum ions to be extremely
low (Law of Mass Action and/or Le Chatlier's Principle).  This will tend to
increase the rate at which aluminum metal of the engine will oxidize
(corrode) thus leading to increased corrosion due to the presence of the
phosphate (again, Le Chatlier's Principle).  This is essentially inescapable.

For your reference, check out the Nernst Equation section of your freshman
chemistry book.  Without going into great detail, it shows that a low
concentration of Al+++ ion (caused by the presence of lots of PO4--- ions)
will have a higher half-cell voltage and will tend to me more reactive.
Also check the section on Solubility Products for an explanation as to why
the Al+++ concentration will be low.  [Al+++][PO4---] = constant where []
refers to molar concentration of the species.

Now, the question is: "So big deal.  How fast is that?"  The answer is, "I'm
not sure.  It may still be pretty low - low enough to make no practical
difference in engine life."  The aluminum phosphate formed, however, will
tend to collect in your cooling system and will more or less NOT flush out.
This could impair the efficiency of heat transfer and reduce water flow
rates thru the system.  Again, "How fast?"  Again, "Dunno".

To be safe, I'd use the phosphate free coolant.  To be cheap, er, uh,
frugal, it may not actually be *necessary*.

At 04:41 PM 1/19/96 -0500, you wrote:
>On Fri, 19 Jan 1996, Robert Myers wrote:
>
>> Agreed, Al.  It's time for a bit of label reading.  If it sez "phosphate 
>> free" is should be OK.  If it sez "Safe for aluminum engines" it should 
>> be OK.  If it doesn't make one of these claims, find another variety.  
>> This should getcha purdy well taken care of.
>> 
>You know... I NEVER used a 'phosphate free' or 'aluminum safe' antifreeze 
>on any of my engines and I never had a problem... What kinds of problems 
>SHOULD I have seen?  Everything from my '71 Fiat spyder....my 4kQ (which 
>got 300K with no probls...) my 90,tqc,80Q...list goes on and on...
>I never thought about it, nor did I ever have any problems.
>
>Sounds to me like a marketing thing!
>
>Bob
>
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	Bob 
********************************************************************
*  Robert L. Myers                        <rmyers@wvit.wvnet.edu>  *
*  Chair, Department of Chemistry          304-442-3358 (office)   *
*  West Virginia Institute of Technology   304-574-2372 (home)     *
*  Montgomery, WV  25136                                           *
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*        My Siberian Huskies like to ride in my '89 200TQ          *
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