Good morning and thank you for your question. I would discourage you from planting vegetables in a galvanized steel container.  Zinc and cadmium and other chemicals from the galvanizing process may leach into your soil.  Also, the container would likely get very hot in the summer and my burn some of your plants.  Here is a factsheet for further reading.  Thanks. 

https://depts.washington.edu/hortlib/pal/growing-edible-plants-in-galvanized-containers/