I just saw this site on Wikipedia. about anodyzing metal:
http://en.wikipedia.org/wiki/Anodizing
It included a paragraph on "Hard-coat" anodizing cylinder bores in alu blocks. The instance they used was in BMW engines. I assume that this same process is used by Mercedes, and maybe all the way back to Chevy's very peculiar foray into the future with the Vega engine. Anyway, it's a clearly-written brief description, if anyone has been wondering. Like anything in Wikipedia, there's no guarantee that it's correct.

http://en.wikipedia.org/wiki/Nikasil

Nikasil caused a lot of problems with BMW and Jag's back in the late 90's. MB never used it AFAIK.

Now fast forward to 07, BMW uses some pretty neat stuff in their new engines. I think the blocks are magnesium, I would assume they would have to line the cylinders in some manner. Either through a coating, or as Mercedes did it with iron sleeves.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The funny thing (if I remember correctly) is Nikasil was originally developed for the Mercedes Wankel rotary engine.

I did a lot of reading years ago about the BMW E38 Nikasil problem and seem to remember mention of Mercedes using it in cars like the 380SL. I may be wrong but I'm sure someone with more info will add to this.

Nikasil was used back in the 60s in the cylinders of air-cooled Porsches, and continued to be used up until?? with no problems.
Mercedes used the "Reynolds Process" in their early aluminum V8s. The same process was used by Chevy Vega with less success.
I have no idea what Porsche and Benz are currently doing with their aluminum blocks.