Hello List Folk,
Just a word to address the anode(sic) idea mentioned in the string on
coolant and radiator technology.
The concept of placing a piece of ignoble (or low grade, relative to other
metals with which it's in contact) metal in solution is not new. Any
chemical system in which two or more dissimilar metals interact will create
a galvanic cell. This means that the more/most noble of the metals will
remain in tact while the other(s) will corrode.
For example: consider a sword with a steel blade, a silver handle, and a
gold hand guard buried since the American Civil War. The steel blade will
be most deteriorated, while the silver will be heavily oxidized and
discolored, but far more complete than the blade. The hand guard will not
only be the best of the three, they will still retain some luster (a
function of surface oxidation) and be in the best state of preservation of
the three.
Apply this to the micro-system which is your Sunbeam radiator: in the
presence of ethylene glycol (anti-freeze) the radiator's copper, brass
and/or aluminum are in a chemical system with an iron engine block. The
radiator, being the less noble metal, will degrade first. One way to
diminish this effect considerably is to introduce a sacrificial object of
metal less noble still, (preferrably one with considerable surface area).
Here's where it gets to be fun: one clasic case where this is done today
is back in merrie olde England where there is tremendous mineral content in
tap water. Enter the tea plantations of the British Empire and you have the
national addiction --ah, tradition of tea, now brewed in purpose-built
teapots of immersion heater style. The pots are plated steel, the immersion
heater coil is usually aluminum, and there are minerals galore in the water,
all heated together to boiling temperature(sound like a radiator yet?)
So the Brits put into their teapots miniature donuts made of stainless
steel strands. The minerals leach out of solution in this electrolytic
cell, and attach themselves to the large surface area of the steel stranded
donut. This saves the heating coil --a less noble metal than the pot-- from
becoming encrusted with minerals, and makes the tea taste quite a bit better
to boot (if you consider British tea to taste good).
And when the steel donut is thoroughly coated with minerals, it can be
discarded and replaced with a fresh sacrificial unit: the teapots of the
realm are preserved.
That's how a sacrificial anode can save your radiator. In an ideal world
the corrosion inhibitors in antifreeze would protect your radiators' guts,
and the aluminum head, and the iron block, but not all corrosion inhibitors
are equally suited to each of the above-mentioned metals. To best protect
your radiator, use the best antifreeze you can find, with water wetter, and
add the sacrificial object --a 3/4" unplated nut suspended on carefully
knotted high test strength fishing line-- and you will have all your bases
covered. When the sacrificial metal object is encrusted, just replace it
with another and carry on.
The realm of *your* radiator will be safe for future generations, all
thanks to a sacrificial nut.
Cheers,
David Kellogg
tea drinker
and Sunbeam addict
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