I'll try to explain it as far as my understanding goes ( I had a year of metallurgy, way back when, mostly on a practical level and not a theoretical level).
The alternator and other electronics in your vehicle introduces various wave forms into the metal (circuit). These can cause a potential (unequal distribution of electrons). The interaction of the chemical components and the electrical components of this process are so intertwined they are inseparable.
Most common cause is an imperfect rectifier in your alternator. But it can also be the electronics in your PCM or someplace else (condensers/filters or capacitors can also cause this. Poor grounds causing an imbalance or just bad luck. . Sometimes it just the balance of anodes and cathodes in the system, dissimilar metals.
Identifying the problem and finding a solution are two different things. Chemical/electrical interactions is a whole segment of chemistry and physics.
Using a quality antifreeze can help. Antifreeze has additives that coat the inside of your motor and radiator. This slows down oxidation, leeching, migration and many of the chemical/electrical processes.
Anti freeze degrades as it ages, instead of a base it gets more acidic (or less base) which can actually accelerate (or inhibit less) these processes.
I know for a fact that automotive electronics cause odd wave forms in the system. Out of curiosity I hooked up an oscilloscope to my Renix. I've seen some really odd wave forms on my oscilloscope.
Copper isn't necessarily the answer (it is often a cathode, but not always). An anode is effectively a pitcher, it tosses electrons and an anode is a catcher, it catches electrons. Leeching is the migration/degradation of dissimilar metals. Copper is often a catcher and not a pitcher, but not always. You may have hit on the magic balance, but in all probability you have just changed the flow of the electrons/leeching/metal migration.
In my 96 the thermostat is in just the right (wrong) spot and disintegrates every few years. I've tried both Copper and galvanized steel. The galvanized steel lasts longer than the Copper. Copper can also be an anode in the right situation.
What I'm saying is a solution can be guess work, Copper may or may not be the answer.
EcoMike would be the best guy to answer this and to clear up any misunderstandings I've acquired over the years and maybe clean up my terms some. My understanding of these processes are mostly on a practical level, trial and error.