Galvanized steel is just steel that has been coated with a thick coating of zinc. In terms of welding, once the zinc coating has been removed and adequate safety precautions have been taken, galvanized steel may be weld just like regular steel. Galvanized steel is more resistant to corrosion than plain old iron, so if you plan to paint the structure where you're welding, give it a shot first. If it doesn't work, there are specialty paints out there that can be used for welding. The only real difference between welding galvanized and ungalvanized steel is that you will need to use special techniques when welding together these materials. Otherwise, use your normal procedures when welding. Be sure to follow all proper safety guidelines before you start welding!