157dB

I deburred aluminum daily for a while there
and the last step was to clean it with Simple
Green (diluted to the proper strength, of course).
It never corroded past the simple surface corrosion
you really want to have. Surface corrosion prevents
any more corrosion from simply being exposed to air.

The only difference I would see is that the engine
could be hotter than the aluminum I was cleaning.

When aluminum rusts, it forms aluminum oxide,
an entirely different animal. In crystal form,
aluminum oxide is called corundum, sapphire or ruby
(depending on the color), and it is among the
hardest substances known. If you wanted to
design a strong, scratchproof coating to put
on a metal, few things other than diamond
would be better than aluminum oxide.

By rusting, aluminum is forming a protective coating
that’s chemically identical to sapphire—transparent,
impervious to air and many chemicals, and able to
protect the surface from further rusting: As soon
as a microscopically thin layer has formed, the
rusting stops. (“Anodized” aluminum has been
treated with acid and electricity to force it to
grow an extra-thick layer of rust, because the
more you have on the surface, the stronger and
more scratch-resistant it is.)

This invisible barrier forms so quickly that aluminum seems,
even in molten form, to be an inert metal. But this illusion
can be shattered with aluminum’s archenemy, mercury

CincyGT2009

And I think the point you made there is the critical part...diluted to the proper strength! I had heard (years ago, when I was active with the Taurus Car Club of America forums) of guys spraying the stuff full strength on their engine bay and ending up with some of their Aluminum parts looking like a splotchy mess.

HillbankMotorsports

+1 on Simple Green. Just make sure you get the concentrate and dilute it if you spray it on any non-cleared painted surfaces. If you are spraying it directly onto the engine and it has a lot of gunk you and use it non-diluted and brush the area and spray quickly for some amazing results.

Roy_R

I don't dilute it, buy it in the Spray bottle from Home Depot...I don't leave it on for more than 5 min max...the spray it down. Haven't used it on the Stang though...too many places for water to collect, lit the sparks plugs, wiring looms etc.

PS. Don't even want to know what simple green will do to my M90???