OK - Now I'm a bit perplexed. Rust - in the sense most of us understand it, is ferrous oxide. To have rust as defined, the door would have to be ferrous. However, please read the following excerpt from the factory Press Kit for the W211 CL Class:
"Body in intelligent hybrid construction using various materials
The low fuel consumption of the new CL is also partly due to the technology of its body, which is based on the selective use of different lightweight materials. Aluminum, magnesium, plastic and steel are the main components of an innovative hybrid body construction system that makes the CL a technological standard-bearer in this field as well. For example, the hood, door paneling, rear fenders, roof and other parts are made of aluminum, the front fenders and trunk lid of high-quality plastic and the insides of the doors of magnesium."
Neither the door interiors, door exteriors or the rear "wings" are ferrous. In fact, it appears that the only steel in the chassis is in places where it cannot be seen. Of course, corrosion can occur in aluminum, the material in question here, but it isn't rust as we normally define it. Disimilar metals will often cause "corrosion" effects and sometimes, in the exotic end of the market where the CL, Ferraris, etc. reside, unexpected problems can arise. I am speculating the the "rust" issue here is from the disimilar materials used and not from the paint, per se. Any connection to problems with the W210 problems is remote at best.
As far as buying a W113 at a very inflated price over a CL500, I don't know. If the only intended purpose for the W113 is to potter about and maybe show the car, perhaps. But if you need to travel any distance at speed, not in a million years, in my opinion. I have 35 years experiance with my W113 and frankly, the chassis dynamics and noise level are reallly starting to show their age. Keep the CL, see what M-B is doing to address the issue, have the coating system fixed. It is a better car in every respect. To further my point, my wife and I had to cover almost 2,000 miles in 4 days last month. Our choice of vehicles was our 250SL or our E430. We took the E430. After two consecutive 14 hour stints we got out of the car completely relaxed, "ready for more". We've done 12 hours in the SL several times, and while it is very comfortable for it's day, we ceratinly weren't "ready for more".
Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex