Rust and steel

I wasn't even sure what forum to put this in.  
My son and I were talking about the garden, he wants to expand it even bigger than what we have. I was explaining that the gophers are so bad, I feel like I need to make hardwire cloth baskets for everything I plant in the ground.  
Both my boys work for a water pump business. When they replace a water tank  it's taken to a place in town, who knows what they do with it. The tanks are steel. They will rust. He asked if rust is harmful to the plants, and, or soil?  It would be free, and simple enough to cut them in half, and put them in the ground. I told him we would need to drill a bunch of holes in it so the worms can come and go.
I have no idea if this is a good idea, or a terrible idea.  I love the idea of making use of something that other wise might end up in a trash heap. I don't want to contaminate the soil, and veggies with steel and rust.
So hope You wonderful people can share your knowledge. Thanks

Personally I wouldn't worry about a little rust in food producing soil. And since it stays right beside the rusting item, it's easy to scoop most of it away later if desired.

I'm not sure about the impact of painted or galvanized coatings though. Some tanks have a baked on enamel that is well nigh indestructible, and if they were rated for drinking water I'm guessing they are safe enough.

If the water tanks are for drinking water, I would suspect the inside *might* be stainless steel, unless lined with some kind of bladder or plastic ....or they might be painted inside with an epoxy-type resin if they are used for commercial/industrial holding tanks. Regular unprotected steel wouldn't last very long in direct contact with water.

Worth a shot in my opinion,  as long as you can get rid of them cost free in the event it doesn't work out for you. I wouldn't be too concerned about rust getting into your soil. If your boys aren't sure what's inside the tank, endoscopes can be purched for approx $40 and you can have a look, something like this for example:

https://www.amazon.com/DEPSTECH-Waterproof-Inspection-Megapixels-Smartphone/dp/B01MYTHWK4/ref=sr_1_5?crid=1DA0O3DQBGQVU&keywords=borescope&qid=1643380133&sprefix=bore+scope%2Caps%2C276&sr=8-5

We have a ton of scrap iron in our soil, since our sandy lime soil is very deficient in iron this is a good thing, people around here use sheet iron to protect newly planted trees from voles. If rust is bad for plants no one has told the plants here.

Do gophers do that much nibbling under ground? Around here we have woodchucks and their damage to my garden has always been above ground.

Thank you all.
My son says there is a rubber, or plastic bladder in the tank.  This would be removed.  We will cut the tank in half so we get two planters from one.
You don't even want to get me started on gophers.  Last year I put in two new hugely beet raised beds. ( Dug into the ground 2 feet. Filled with old fire wood, soil, branches, compost type stuff like leaves, veggie scraps, shredded cardboard, soil, wood chips, soil, organic compost and organic soil. Used cement blocks 2 high ending up about 16" above ground) I planted, and it was a dream year. Everything growing and producing better than I have ever experienced. In a matter of a week everything in one bed was dead, and about 50% of the second bed.  Mostly the gopher would eat the roots you would see a dead plant and lift it up and see no roots. It actually pulled a hole jalapeno plant into its hole.  I also lost an apple tree that had been in the ground for a year.  We have always had gophers, but never the devastation of last year.  I think maybe with the severe drought, watering drew them in, I don't know. I just don't want to go through it again.   I put hardware cloth at ground level on my raised beds, and trying to find ways to protect what I plant this year.
Thanks again. I think I will tell my son to bring the next couple home.  It seems like it's worth a try.

I think it's a great idea. I rather have rusty than galvanized since a lot of galvanized things will leach lead into the soil.

Jen Fulkerson wrote:My son says there is a rubber, or plastic bladder in the tank.  ...
I think I will tell my son to bring the next couple home.  It seems like it's worth a try.

The bladder tells me that these were pressure tanks for water wells or similar. The bladder is the "spring" that maintains pressure. I agree, definitely worth a try. If coatings are a concern, it's effective (though not refined) to throw them in a fire in a non food growing area. Or hit them with a tiger torch and peel it off.

Jenny Wright wrote:I think it's a great idea. I rather have rusty than galvanized since a lot of galvanized things will leach lead into the soil.

galvanized should contain almost zero lead simply because of how zinc is produced.  The basic chemistry of producing pure zinc will not allow the lead to transfer also.  There are basically 3 methods for getting zinc or zinc alloys.  There is some risk in using copper or other metals as the reducing agent to make brass or other alloys, as the lead can move over that way.  But pure zinc is recovered as a condensed gas in a process that should transfer basically zero lead or it is done by flotation separation and then it is electrolytically refined and the electrolytic refining should also transfer basically zero lead.   Another measure is how many galvanized things are used with drinking water for people and animals.  Piping and water tanks etc.  Which also says they expect it to be clean of lead.

That said most water tanks that are steel will be glass lined steel(mostly gas fired with some electric) with a few galvanized tanks usually used for hot water storage rather and some will be composite materials such as fiber glass(which are all electric tanks).  Since you can easily separate the steel tanks with a magnet that is easy  So there will likely be tiny flakes of glass left over after the tanks rusts away.  But the glass liner is used because it is highly chemically inert.  I would be more concerned about the coating on the outside of the tank.  Most are standard black oxide finish and it should be safe and some are glass inside and out which also should be safe.  Iron, zinc are something most soils are short on and the glass flake should be harmless because of how thin it is.  But some tanks have a paint type coating on them and I would be concerned about those.   No idea what makes up the paint type coating.   We used to build culverts out of water heaters by cutting both ends off and welding 4 to 6 barrels together so I have cut probably nearly 100 tanks up.  Be aware that many tanks will be 1/4 to 1/2 full of hard water deposits because of poor maintenance of the tank.  This you will likely want to get ride of.  Mostly it is calcium and magnesium carbonates.  Some of it when you get it burning makes a nasty fire though.  Also most have an anode rod and it makes a nasty fire too.  Now a few rare water heaters are stainless.  Hang onto these for other projects when you find them.  As they were way more costly, mostly they are only used in commercial settings for the added reliability and almost never end up in scrap piles.  Most will be 304 stainless which is magnetic but the outer finish will look like plain steel rather than being dark black oxide finish or painted looking so there again separation is fairly easy.