Engine finish?

[Jim Garfield]

Does anyone know what technique the factory used to achieve this finish on their more exotic engines? Is it the coating that Dow makes?

edit: Sorry, I meant for this to be in off topic.

[304065]

Jim,

That brown color is characteristic of a process known, alternatively, as "Dow 7" or "Alodine" or "Iridite." It is a conversion coating that works only on Magnesium. This is why you only see it on exotic stuff like 917, 906, etc.

Hope this helps. It would not be correct for 911 stuff.

[Jim Garfield]

Thanks John. I was just curious if that was what the Dow process looked like on Mg. I wonder how it would hold up on Mg wheels? Probably not great.

[304065]

Jim,

It would be better from a corrosion and appearance standpoint to first apply the conversion coating and then topcoat with paint or another finish. In the case of something like a fan, a coating such as electroless nickel might fare better over the long term.

[Tom F.]

Thanks John. I was just curious if that was what the Dow process looked like on Mg. I wonder how it would hold up on Mg wheels? Probably not great.

I think that Dow 7 was invented for magnesium aircraft wheels.

[Jim Garfield]

I think that Dow 7 was invented for magnesium aircraft wheels.

Hmmm, that's interesting. I can see that I'm going to have to do some research about the process. I remember reading about it years ago but I don't recall many of the details. I wonder why Porsche didn't use it on all of the Mg bits?

[CurtEgerer]

... like my 901 gearbox case which is beginning to approach the porosity of a sea sponge

[RPMClassic]

Seriously, is there any reason why you couldn't do the exterior of an entire gear box or engine case? It would sure be the solution of old minilite wheels and coke bottle wheels that are getting nasty at this point.

[Flunder]

This image is of a freshly treated magnesium 915:

[Tom F.]

This image is of a freshly treated magnesium 915:

Treated with what?