There are a number of models built in the last decade that have excessive corrosion and deterioration to the rear subframe, the R231 being one. Here's a link that discusses everything on another forum (I could not find any discussion here):

W204 rear subframes deterioration | Mercedes-Benz Forum (benzworld.org)

There is a service supplement addressing this: MB Service Supplement Document regarding rear subframes: S135.00-P-0009A

Is there any evidence that this issue applies to our R231's and if so does it apply to all model years?

Yes, the R231 is included in the service bulletin. I will post the list when I get home. I have not been able to fine a copy of the bulletin yet, but will keep looking.

S(I)35.00-P-0009A

More likely in areas using snow melting chemicals? If yes, glad my car spent its earlier years in Florida. I wonder if this is something the dealers are supposed to check during routine maintenance? I plan to ask on my next visit in May.

Thanks for posting, JettaRed.

Correct, Type 231 is included. I’d like to see the English version.

Nein, es gibt keine Englische Version

JettaRed, Hagerstown has a German Service Writer. Name is Alex Foltz. Nice guy.

Mid-Atlantic state (PA, NJ, others) inspection will catch some rust and workshops are well-practiced in welding small repair pieces in place. Much less expensive than replacing a subframe.

If your vehicle is not subject to state inspection you would need to ask the dealer/Indy to check it and come up with a solution. Welding is not something most dealers like to do, except for the example given above where I have first hand experience with getting patches welded for state inspection.

To keep this in perspective, there are no known instances for the R231.
This is a note to check for rust during rear axle maintenance, not a service bulletin.

Not trying to create panic, but just making folks aware of a potential problem.

Here is an English version for us mono-linguistic types.

Makes sense but keep in mind that it is a supplement to maintenance notes and covers a whopping 21 Model years (2000-2021)...

The Service Instruction is available in the WIS/ASRA.

My 2014 E350, dealer maintained, 60k miles is at the dealer with a corroded, cracked subframe issue. I just spoke to these class-action attorneys and suggest anyone with this issue do the same. Reach out to these attorneys, who are investigating a class action against Mercedes. They were part of the firm that sued Mercedes for climate control issues.: Katan Patel:kp@corpus-law.com and Muriel Kenfield-Kelleher: mkenfieldkelleher@lchb.com 678-597-8020

Actually, corroded R231 subframes (scrapped) are being talked about on cars in England.

How TF is an aluminum car experiencing severe corrosion problems?

because the subframe is mild steel not alu

An extended warranty has been issued (Feb 8th ?) that covers corrosion PERFORATION in the subframe for 20 years.
https://cimg8.ibsrv.net/gimg/www.mbw...5455cd4b05.png

🤦🏼🤦🏼🤦🏼

Does this mean the 2018 and newer SLs don't need to be covered and if so why; are the 2018 and newer years built with better rust resistant materials or what??

Have you ever come across a thread that sounds interesting and when you open it you discover you started it? 🤦‍♂️

LOL

Yeah but, Montreal's attachment states only for MY 2013-2017 SLs so........looking for answer to:

Is there any evidence that this issue applies to our R231's and if so does it apply to all model years so it will cover my MY 2018?

Have yet to hear, or read one R231 that has had this issue. But maybe if you use it as a taxi
That being said, yes it applies to R231 as it's listed in the TSB.

Seems to be prevalent in C and E class models.