Is the Mycelium HD wallet private key stored encrypted on the device? haven't found details on that in the net.

My concern is that I'm using a corporate (bring you own device) phone. We have to install a "security" app running with administrator rights. 

IMHO this app can read EVERYTHING what is on the device. I'm pretty sure. Therefore, is the private key of the Mycelium HD wallet encrypted (with the PIN hopefully) when stored the device?

Any thoughts?
Yes, Mycelium stores an encrypted copy of your key, protected by your PIN (if applicable) on the device. This includes any individual private key accounts you import.

In general, I would advise against storing crypto keys (or any private keys or confidential information, really) on a corporate device (laptops, phones, desktops, email accounts), or even a device others can access regularly.