Thank you for writing.

Galvanized steel is a fine material for raised garden beds.  The only caution is that acid oxidizes it. See 4-101.15  https://www.oregon.gov/oha/PH/HEALTHYENVIRONMENTS/FOODSAFETY/Documents/foodsanitationrulesweb.pdf

Here page 1,9. http://solanomg.ucanr.edu/newsletters/Seeds_for_Thought64596.pdf

The principal question if you are using pre-owned galvanized bins is whether they were contaminated with herbicides, pesticides, or petroleum products.  Shop carefully, clean any pre-owned  industrial or agricultural material with a pressurized hose system.