Generally speaking, yes a weld build up is an acceptable approach. For a less general response, you'll have to get more specific about material of construction, fluid, code of construction and repair, jurisdiction, etc.
How deep is this pitting?
What's the nominal plate thickness?
Approximately how much of the shell has this pitting?
If you're still above T-min, you should look into mitigation by coating the shell.
A lot of our gasoline tanks have that GENERAL pitting throughout the entire shell and floor. Usually, it's not bad enough to have to repair, but would be at the next interval. To mitigate, we coat.
