Attached to metal or not galvanized steel will rust when exposed to weather.

Galvanized steel just rusts more slowly. It needs to dry out. Look at the base of any galvanized railing where it's embedded in concrete. Rust.

If they are not rusted through you could clean them and paint . That looks more like water problems then metal to metal corrosion, maybe soil composition?

Okay, it looks like my pictures showed up but not my comment. So I’ll try again. These are the pictures of our house before we bought it. It is hard to see but the window well has an area that corroded enough dirt was falling through. Our inspector said that when the well was attached to the house it must have made contact with rebar in the basement wall. This created an electrical current that caused the corrosion. (If I am understanding what he said correctly.) The house was only 11 years old and the other well was fine. We made the sellers replace it. As you can see there was a brand new concrete patio that butted up right next to it and it was partially covered with a wood deck. The cost to remove and replace (including deck and patio) was only $2,000. This was 2 years ago. We also live in Colorado in an area where nearly everyone has basements.

Well, my first comment did appear so sorry for the double post. I will add that the sellers, and both real estate agents were surprised that my husband and I were adamant that it was replaced. They didn’t think it was a big deal so you may find buyers who think the same. Our well wasn’t replaced until the house was sold. The title company keep some of the money from the sell to pay for the work.

I reread your post and saw yours are 90” deep, ours are only 60” but $10,000 still seems like a lot.

tdemonti Code says there must be 36" clearance from wall of house. Wish that we could as ground in Arizona is very solid..

Anita, Thank You for sharing!! Good that you insisted upon repair as the corrosion becomes worse very rapidly.

I work in the steel industry, and I'm pretty sure that the rebar wasn't the issue. Years ago when they made guard rails, an entire coil of steel would be galvanized, then sent out to be formed. This caused the guardrail to have an exposed edge. Fast forward a few years and guardrails started to fail. The exposed edge was allowing the guardrails to deteriorate from the inside out. During inspection they looked fine because the galvanized coating was doing it's job, but in the opposite.

Now they form the rails, drill the holes, ect, then dip them in the galvanized coating. This is more than likely the issue with you wells. There were exposed edges/screw holes, ect and they are rusting from the inside out.