This is my go to explanation for things concerning chemistry and chickens. Have you ever read one of those far fetched sci fi books or watched a movie where the alien population has corrosive blood or breathes in a horribly corrosive atmosphere? Well, that is actually earth. Oxygen is a horrific oxidizer. An oxidizer is a chemical or substance that strips electrons from another substance or element. Fire is a fast oxidation as are explosions, rust is the same just much slower but it generates the same amount of heat over time.
Most metals are not found on earth in the pure form because........ oxygen has reacted with the metals to form an oxide form of the element. Ferrous oxide= rust which is the natural form of iron. Ditto on zinc, while the most common form in nature is Zinc Sulfate there is a small amount of Zincite or Zinc Oxide found in nature.
The point being is that most metals are not in their natural state and will immediately begin oxidizing or combining with other elements like sulfur to produce a non pure more stable version of the original element.
What you can do is check the pH of the water that you are putting in the feeder. pH is a measure of how acidic or how base (think alkaline like lye, on the other end of the pH scale) a substance is. The closer the water or other substance is to pH neutral, 7 to 7.2 low range, the less corrosive the water is. pH is a count of the amount of hydrogen in the water or substance, acids are high pH, alkalines are low pH. So it is more than just oxygen and sulfur that is trying to dissolve metals and other substances starting at the moment they are purified into a useful state.
You can adjust pH easily, google is your friend, but even with perfect pH the oxidation and sulfurization will continue. Swimming pools and water treatment plants monitor the pH levels for this very reason as well as aquaculture. Varying the pH makes some heavy metals more bio available too which isn't a good thing.
