Chromium (VI) under the hood (part II)
- Markus Sommer
- Jul 17
- 2 min read
A completely normal car with an exhaust aftertreatment system, calcium-containing insulation materials, installed in an “oxygen-open” manner.
These are ideal conditions for the formation of carcinogenic chromium (VI) compounds (chromates).
Chemistry doesn't lie! Not even in the engine compartment.
Initially, the so-called "metal hot parts" of the exhaust aftertreatment system were provided with welded integral insulation; the component was covered with an insulating material and then provided with a protective foil, which in turn was welded to the hot part to ensure a tight joint.
Over time, it was time for savings, because the integral dam had to have the hot part with him in order to be able to carry out the above-mentioned process, which meant a high logistical effort.
So the idea came up to develop half shells that could be attached directly during final assembly at the vehicle manufacturer.
The half shells were manufactured as a sandwich, delivered directly to the car manufacturer and could be assembled in just a few steps;
Welding was no longer necessary - simple clipping and folding of an assembly seam replaced the previously complex welding process.
However, this concept, which in principle makes economic and logistical sense, has a crucial disadvantage: it is “open to oxygen” and thus susceptible to the thermochemical reaction of chromate formation, as the chemical process is only possible with additional oxygen from the ambient air.
But the problem becomes even more complex, because calcium-containing insulation fibers detach from the half-shells and the heat flow "blows" them out. Then the fibers can settle everywhere, unfortunately also on non-insulated stainless steel hot parts, and then the chromate formation also takes place there, as the video impressively shows:
The affected vehicles?
All car and truck engines that have such thermal insulation (heat shield).
The consequences are impossible to estimate, as there are no threshold values for chromium (VI) compounds. This poses costly challenges for auto repair shops and service centers, as chromates are skin-absorbing ("h") and, according to TRGS 401, the high risk range applies even to small amounts and short dermal contact times.
Another hurdle is the H410 classification of chromium (VI) compounds, the highest environmental classification available.
Even asbestos fibers or glyphosate are not classified as H410, but arsenic and mercury compounds are.
We will inform the relevant professional association and other authorities of the latest findings and will update the progress of this worrying news here.
If you find such insulation with oxygen-open ends in your vehicle, please be careful!
Your dealer and service center, as well as the vehicle manufacturer, will probably try to downplay the issue; don't let them put you off or deceive you!
Vehicle photos: MB E220 bluetec (Year of manufacture: 2018)
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