Corporate debt is always less secure than a government's, because governments have the power to forbid companies in their country to pay their debts - both to external creditors (as the multiple debt crises and convertibility/transferability restrictions have shown) or even to internal creditors (the major innovation of the Russian moratorium in 1998.

Gazprom had a better rating than Russia when it was using its gas export contracts as collateral, because the only way it could default on that debt was to stop delivering gas, a much more violent step nowadays, diplomatically, than just defaulting on payments.

That's why we were happy to lend money to Gazprom, effectively taking Gaz de France risk while being paid margins sized on Russian risk (then - Russian risk today pays very little). Ah, good ol' times...

In the long run, we're all dead. John Maynard Keynes