Yes. The angel's immateriality is the cause why it is incorruptible by its own nature because if the form subsists in its own being, as happens in the angels (A2), it cannot lose its being.
When it is said that all things, even the angels, would lapse into nothing, unless preserved by God, it is not to be gathered therefrom that there is any principle of corruption in the angels; but that the nature of the angels is dependent upon God as its cause.
For a thing is said to be corruptible not merely because God can reduce it to non-existence, by withdrawing His act of preservation; but also because it has some principle of corruption within itself, or some contrariety, or at least the potentiality of matter.