I was pretty amazed. This has
been going on for a long time, for collectors of everything from old
trains to radios and old machinery that use ZAMAK for castings.
I'd
say enjoy the letter, but if it's happened to you, you know it sucks.
As an aside, there is a process that might delay the decay, but it's
based on a chemical called Parylene, and you'd have to apply it in a
pressure vessel - after stripping the paint and removing any plastic
pieces. Expensive, and totally destroys any originality of the piece in
question.
Hope it helps to explain the problem. I checked my
stuff very closely after doing the research. So far, so good - only one
or two models that showed any signs of decay, and they buffed back to
brand new.
Here's the letter, and my reply.
Dear Editor:
I have been collecting die-cast cars for several years, but now I may stop collecting them.
I
have two 1964-1/2 Mustang convertibles made by Revell, one of which is
the Indy 500 Pace Car. The other one is identical to the one that is
pictured on page 50 of Toy Cars & Models August 2003 issue. The print says,
"Revell's older 1964-1/2 Mustangs are worth seeking out in convertible
or coupe form. Look for several 1960s colors, too." My suggestion is
not to buy any of them.
I bought mine new and kept the cars in
their boxes because I wanted them to remain in new-looking,
unplayed-with condition. A passing glance at the red convertible
revealed something odd. I took the car out of the box to look closer at
it. It looked like it was melting. All corners of the hood were curling
up, the hood had cracked in half, stress cracks appeared everywhere. I
tilted the base the car was mounted on, and both doors fell off. The
paint is crazing and bubbled. The car is broken everywhere because the
casting is so brittle. I immediately took the pace car convertible out
of its box to check it out, but it appears to be OK. I can only wonder
if it will soon fall apart, too, since it is from the same casting as
the other one.
I thought these cars were supposed to last - that's
why I bought them. I feel Revell should make good on these cars and
give a refund to anyone that bought them, even if they are old. I can't
afford to replace them if this keeps happening. Right now I'm not
working.
Please tell everyone to pass on these cars.
XXXXX XXXXX
Capay, Calif.
Hello, XXXXX –
Thanks for writing. First,
the good news: you needn’t worry too much about the untimely demise of
that Revell Pace Car. Unless the two models came from the exact same
batch of metal (not just the same mold set), you’re probably cool. Now,
the bad: The problem happens to cars from virtually every maker, and
attacks with almost no warning. Even worse, once it starts, you can’t
do a thing to stop it.
Your old Revell model fell victim to an
extreme case of “intergranular corrosion”, a phenomenon that occurs in
castings made from
ZAMAK – the stuff diecast cars are made from.
ZAMAK
is a hypoeutectic alloy of zinc and approximately four percent aluminum
(more aluminum than that, and the alloy is called “hypereutectic” – and
loses its ZAMAK name), as well as a few trace metals.
Those trace
metals can be part of the problem – but more on that in a minute.
ZAMAK’s been around since the early 1900s – some say as early as 1896.
The reason it became such a popular material is that it’s tough,
relatively inexpensive, and it can be cast into very detailed shapes.
That’s made it the material of choice for industrial applications – as
well as metal toys – pretty much from the beginning.
I was moved
by your story, and it’s one I’ve heard from several collectors over the
years, so I decided to do a little light reading on the topic. What I
found was:
There is no such thing as “light reading” when you’re discussing metallurgy;
The problem is so prevalent that there are actually scientific papers published on it.
Yes,
it’s true.
So I refer you to document NLR-TP-2005-205,
“Corrosion-Induced Cracking of Model Train Zinc-aluminum Castings”
(R.J.H. Wanhill and T. Hattenberg, National Aerospace Laboratory NLR,
May 2005), probably the most comprehensive study yet undertaken in an
effort to explain what happens to our prides and joys when the lights
are out and nobody’s home.
After reading the paper (which almost caused
“intergranular corrosion” within the wrinkles of my brain), I learned
that the presence of lead (Pb), cadmium (Cd), or tin (Sn), in amounts
that exceed approximately .005 percent by weight, will pretty much send
a diecast train – or your model car – to the dustbin without so much as
a how do you do.
The rate at which this does or doesn’t happen
depends on the level of metal contamination – and moisture. And heat,
since you’re asking. Warm, damp places will accelerate the evil deeds
done by those filthy metallic stowaways, which get into the dendrites
(crystals formed within the alloy as it cools) and start a reaction
that causes the metal to literally come apart at its molecular seams.
This is why I never store my models in my mouth. Though I’ve been told
they’d probably fit.
Brauer & Pierce examined the phenomenon
in 1923, and I’ve had firsthand experience with it on a pair of
Ertl/Supercar Collectibles COPO Camaros on which the doors abruptly
turned to dust – after years of what was considered “safe” storage in
their boxes.
While there’s no way of predicting which models will
self-destruct, there is something you can do to help prevent the zinc
termites from chowing down on your collection – wax it. It’s been shown
that the models usually deteriorate from the outside in, so keeping a
good polish on hand and giving the cars a once over every now and then
might be a good idea. Yes, that means taking the cars out of their
boxes. But if you keep all the original accouterments that came along
with the model, you can still get top buck when you want to sell or
give the car away. And, you might even actually get to enjoy the thing.
Just my opinion.
So, you see, it’s not a Revell problem. Revell
makes some great stuff – just ask my credit card. So, if and when you
can do it, you might pick up another of those little ragtops. But, as
with any model of any vintage, I’d advise you look for telltale signs
of bubbling or large pits in the paint before you plunk cash on the
barrel.
Good luck – and happy collecting.
About the author: Joe Kelly Jr. is a DCP member and avid collector who writes a regular 1/18 scale column for Toy Cars & Models magazine. Joe also is an avid
slot car enthusiast. Check out his unbelievable setup that hides on the ceiling when not in use.
Joe Kelly slot cars
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