Best way to Clean (exterior) a 914 Transmission, I am about to have it Evil rebuilt (third one is a charm) and want to Options

[Cupomeat]

Any tips/advice for cleaning the exterior of a transmission?

I scraped and got most of the obvious road dirt off it last night, but I'd love to paint this one after it gets back from Doc. Evil's GearBox Summer camp. (IMG:style_emoticons/default/351.gif)

I am afraid to use a pressure washer for fear of water ingress, and obviously, the least amount of chemicals the better.

Thanks

[Katmanken]

A coupla points:

First:- About mag corrosion from the internet....

"And while the corrosion rates of modern, high-grade magnesium alloys are acceptable for interior applications, the automotive exterior environments are extremely harsh for bare and even coated magnesium parts.

The interface between the steel bracket and a magnesium-alloy casting is prone to galvanic corrosion.
First, road salts and slurries can easily damage conventional electrocoat paints, creating sites for rapid electrochemical dissolution of magnesium. Second, being the most reactive (or anodic) metal in the electrochemical series, magnesium is prone to severe galvanic attack when in contact with other metals. In automotive structural components such as engine cradles, road salts and debris can accumulate around the bolts and washers that mechanically affix magnesium parts to the car frame. Such sites may become prone to galvanic corrosion (see Figure 2).

Therefore, finding cost-effective solutions for protecting magnesium alloys from corrosion has become paramount.

One of the best ways to combat galvanic corrosion of magnesium is to use isolation materials to prevent direct contact between bare magnesium and the dissimilar metal. If a high torque load is required, such isolation materials must be made of special metals or other inorganic substances that minimize excessive deformation upon loading. In particular, the use of aluminum washers can significantly reduce magnesium corrosion; however, the effectiveness of such corrosion protection is directly related to the chemical composition of the aluminum washer being used (see Figure 3). "

Now for protection:

My mag book suggested elements higher in the periodic table such as zinc to act as a sacrificial anode...

And according to the pelican 911 board....

The Factory Workshop Manual (Vol. I, page SR 140) sez:

“Warning:
Pressure cast parts must not be cleaned with acid, since acids attack the magnesium alloy. After any transmission repairs during which the one-season underseal is washed off the gearbox housing, or when the underneath of the vehicle is washed, we recommend that corrosion protection be improved on the pressure-cast gearbox housing by applying a bitumen or wax based one-season underseal, e. g. Tectyl, which should be sprayed or brushed on.”
© Dr. Ing. h.c. F. Porsche Workshop Manual, Vol. I, Page SR 140.


Tectyl in the wax formuation sounds a lot like cosmoline- the honey colored wax based wax protective coating that''s been around since at least WWII. A lot of european cars are shipped coated in "cosmoline" for protection and it's cleaned off with mineral spirits and a rag. If they didn't clean the tranny, that would explain the coating.

I'm sure there are other wax cosmoline or panel wax materials that look like the Tectyl....