Regarding the calculation, the size of support is acceptable.
However, we still require painting for those support.
With bare steel, corrosion will take place very quickly especially at water area (lower than 1.5 m of the tank).
We suggest you to paint the support ubtil finish then you can repair the paint after weld and installation.
Paint repair shall be done as much as possible. The location that can be access shall be repaired.