Mercedes E class MOT failure <sob>

[footman]

I very much doubt Merc will issue a recall over here, but they may be forced to in the US.
Our systems are very different.

Merc UK are known to be unpredictable over whether they offer a goodwill FOC replacement for corroded subframes, USA and Canada have class actions in progress but strangely Mercedes Canada did issue a recall in 2022 for corroded subframes for specific vehicles.

Transport Canada Recall - 2021772 - MERCEDES-BENZ - Canada.ca

recalls-rappels.canada.ca

 

[footman]

why they corroding? made of pure uncoated iron?

AFAIK the subframe is made from pressed steel but I don't think that in itself is the problem.
The issue seems to be twofold, firstly the quality of the steel has been called into question and also the quality of any rust proofing is being criticized.