A very nice work done with zinc rich cold galvanizing primer. The 3 steps for killing rust on welded area:
- Grinding carefully on surface until all rust & weld lines removed; a shinning metal exposed.
- Use a air jet to clear all the small particles.
- Apply those Cold Galvanize Primer on surface. ( needed to get the job done within 3 minutes. Otherwise, moisture will trapped between primer & metal surface)