The biggest concern I have is the potential high levels of zinc that may occur due to the galvanization process. To galvanize steel it is basically dipped in hot, liquid zinc. The out side of the sheet is basically zinc and the zinc level gradually decreases until the center is again 100% steel. Zinc does not corrode as fast as steel but it will gradually release zinc to the soil. Zinc is needed by plants but excessive levels can be toxic and it will also hinder the uptake of other needed micro-nutrients. Go to http://www.spectrumanalytic.com/support/library/ff/Zn_Basics.htm. This will be a greater problem for plants growing next to the steel but will eventually spread through the bed as you work the soil.

I would rather see you use treated wood or wood composite materials. The price will be higher but less dangerous to your plants.


Ron Goldy

What about placing plastic sheeting (like the kind used as weed barriers in landscape beds) between the metal and the soil? I've seen that suggested on a few forums. Also, wouldn't it take several years for the zinc to get into the soil in amounts large enough to worry about?

Weed barrier is not water tight and eventually the zinc would move wherever water moved. Yes, it would take several years for the zinc levels to become an issue. What will you do then? Remove the soil and start over? That is an option.