It sounds like you have hard water. I have a well and I know my water is hard. You used to be able to purchase a special filter that went on the top of a common soda bottle that would eliminate the minerals in the water. I recently purchased one of those Olso irons. I noted that it had a plastic water holding tank. That would eliminate the corrosion factor while storing the water.
In my youth I worked in a medical lab that had a machine like a large coffee pot that produced such water to use in our testing procedures. They used to sell it in stores just for your "steam" iron. I am having a bad "brain fog" moment and can't remember the term for the water.