[DeTomaso] Aluminum Pulleys Hard Surfacing or Anodizing

[Chris Difani]

Guys:

Just a short note on aluminum, and hard surfacing, or hard facing, or, (the 
real label) anodizing, Type 1 or Type 2.

To harden the surface of aluminum, it's anodized. That's a fancy name for 
creating oxides of aluminum on the surface thru an electrochemical process. 
That compound is better known as "aluminum oxide", this is the same material 
as is used to make grinding wheels, sand paper, and other really tough 
abrasives.

The aluminum oxide is formed on the surface of the aluminum during the 
anodizing process. The depth of the treatment, and we're talking ten 
thousandths of an inch here, is what defines the Type 1 or Type 2 anodizing. 
Also it's simply a matter of time in the anodizing bath that determines the 
depth, which determines the Type. The longer, the deeper, the harder....

.......and yes, I know that's a straight line for some of our readers..... 
who shall remain nameless....

The depth of the anodized layer on the Type 1 is about half a thousandth, or 
0.0005". The Type 2 typically is 0.0010 to 0.0015" thick.

The anodizing process is also the electro-chemical process that gives 
aluminum all those colors. This is simply the addition of a dye into the 
anodizing bath. You can anodize without the dye colorant, or with. You can 
get the Type 1 or 2, with or without the dye. In fact, there's a very simple 
process to do this "at home". If the part is small enough, you can boil the 
part in a water solution. There's a chemical added to the water, then you 
bring it to a boil, then you drop the part in the boiling solution, 
suspended so it's not resting on any surface, and boil for 10 minutes or so.

As you can tell, not rocket science. This while a form of anodizing, does 
not let you color the aluminum. Coloring takes an electro-chemical process, 
which while not that complicated, is beyond the scope of this email.

The other thing about anodizing is that the surface will "grow" in size. An 
aluminum part that's hard anodized will typically be half a thousandth 
larger after the process. The anodizing process causes a crystaline 
formation to occur on the surface (that aluminum oxide stuff), and that's 
where the dimensional growth occurs. This factor is sometimes used when a 
machined part comes out  undersize, and needs to be "fixed".

And now you know all there is about anodizing, and aluminum.

Well, not quite. If you have an anodized piece, and you want to remove the 
"color", all you do is boil it in water that's had lye added. That will 
remove the anodized layer, along with the color. You'll have a chemically 
clean aluminum surface when you pull it out of the boiling water bath after 
10 minutes or so.

And now you know all there is.....

.... as always, your milage may vary, I may not know what I'm talking about, 
you may not know what I thought I was talking about, I may not know what I 
thought I heard that I was thinking about talking about.... etc.... etc... 
yadda .... yadda.

Chris

Chris Difani
'73 L #5829 "LITNNG"
Sacramento, CA
Email: cdifani at pacbell.net







----- Original Message ----- 
From: "Daniel C Jones" <daniel.c.jones2 at gmail.com>
To: "P-car group list" <detomaso at realbig.com>
Sent: Wednesday, June 14, 2006 3:04 PM
Subject: Re: [DeTomaso] Aluminum Pulleys


>> All 11 of my pulleys and idlers are aluminum. A word of caution,
>> however, aluminum is soft and I don't believe it holds up well
>> without being hard surfaced. I had all my pulleys hard surfaced
>> and they seem to be doing OK.
>
> I've heard that untreated aluminum pulleys wear quickly.  I believe
> March makes there pulley out of 6061-T6 and hard coat the wear surfaces
> (to 65 Rockwell "C" scale).  A local guy is making some custom pulleys
> out of 7075 and then dipping them in some sort of surface treatment.
>
>> I can't see any advantage to having aluminum pulleys.
>
> I need a second set (keeping the first set for the backup motor) and
> thought I'd save some weight.  That cast iron crank pulley is heavy.
>
>> You may have trouble finding an aluminum water pump pulley.
>
> March shows aluminum water pump, crankshaft and alternator pulleys for
> the 351C.  They make a couple of sets, one that underdrives (relative
> to OEM Ford, not the Pantera) and one that overdrives using a different
> size water pump pulley:
>
>  underdrive set
>    crank pulley       5 1/2"
>    water pump pulley  6 1/4"
>    alternator pulley  2 11/16"
>
>  overdrive set
>    crank pulley       5 1/2"
>    water pump pulley  5 1/4"
>    alternator pulley  2 11/16"
>
> Dan Jones
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