TorFlex Axle to Frame Weld Repair

[cboss]

I repacked my bearings a week ago and noticed some weld joints failing. Took it to the local weld/frame shop and he hooked me up. There were eight joints bad (I have 22K on the camper). He re-welded them all and it looks good.
My question is: Just paint (Rustoleum) or undercoating?
I'm leaning toward just some paint as undercoating can hold moisture.
Here's some pics before the repair:

[Iwannacamp]

I would use a decent paint. You can see any future cracks...God forbid.