The disadvantages of not treating the closed circuit water can be equally troubling for the system operator:-
1. Leakage in PHE and AHU due to corrosion
2. Plugging and clogging of tubes and reduced flow rate
3. REduced heat transfer
4. Need of regular descalling that incurs shutdowns, loss of labor and time
5. Fouling of brine of chiller water

Chemical tratment removes dissolved oxygen that cause oxidation of metal to metal oxide i.e., Iron + Oxygen = Iron Oxide (Rust)

The chemical also contains a specific inhibitor to protect copper from corrosion and removes/prevents any sort of scale formation in the system.