If your employer's contract permits personal use, then it is permitted. If not, then it is not. Some contracts provide two codes and others simply authorize the corporate code for personal use.

Don't use a code when it is not within scope as that may void not only insurance taken through the contract but third-party as well (as you have certified -- falsely -- that you are entitled to the rate. Not an issue until and unless someone gets hurt or the vehicle is damaged.