Antioxidant vs other additives?
 

There are a dozen water additives that claim to prevent corrosion, but many of them just fight fire with fire by pre-corroding the metal.

Has anyone considered adding a chemical to the water that bonds with oxygen? I tried to find such a chemical online, but was deluged with millions of links to medications and herbal crap.

Point is to dump in some antioxidant, then seal the system nice and tight. No oxygen, no corrosion. (Barring some electrolytic reactions) It should work for a while, and the occasional flush and refill will replenish it.

If your gonna flush and fill your coolant periodically than don't you think finding such an additive would be overkill? You can avoid corrosion by making sure you don't mix metals, and by making sure the water system is securely grounded. Another solution would be to avoid bright light shining directly to the water system for long length of time as it is said to be a result of algae build up.
The additive your looking for sounds like something that would be used in the medical field or in a laboratory.

You could always ditch water and start using fluid xp.

Whats the best way to ground the water loop Mars?

Hydrogen.... :)

Hydrogen only binds with oxygen in a fire or fuel cell membrane.