If you are afraid of your government defaulting, then you also have reason to fear that your country's so-called "AAA" corporate bonds might not be a safe investment. When governments default, they often do things like:
- Confiscate their subjects' financial assets. This can include directly seizing corporate bonds, and/or taking away the assets that the corporations were relying on to pay their bills.
- Increase income taxes and other taxes. In extreme cases, this is not much different from confiscation.
- Inflate the currency. This reduces the value of both government bonds and corporate bonds (that are paid in that currency).
- Impose price controls. This can prevent corporations from doing business.
- Impose "bank holidays", which can prevent you from receiving payments on corporate bonds.
- "Borrow" and/or confiscate local government cash reserves.
- Delay payment of government obligations. This can cause corporations to go bankrupt.
- Refuse to pay government obligations, or insist on a "cramdown". This can also cause corporations to go bankrupt.
In these scenarios, it is not predictable whether government bonds will suffer more or less than any particular corporate bonds.
You might want to diversify into precious metals, foreign currencies, and/or foreign securities. For the most security, you might want to choose investment vehicles that your government would have a hard time confiscating. Of course, you will face currency fluctuation risks if you do so.