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If you're worried about damaging the heads drain the coolant out once a year and refill with coolant/distilled water. It's only a problem when the PH becomes acidic. Keeping it fresh will keep your aluminum parts from getting damaged. If you really want, you can pull the plug on the side of the block and get it all out. But I just drain the radiator every year before I put the car away for storage and it works just fine. I might be concerned where the eroded zinc is going in my cooling system...

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I change once a year now , did one of my cars yesterday.

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while that might work, the acidity of the water is not why it works.

the issue is when the fluid becomes conductive.
distilled and coolant mixed are not conductive to electricity.

stray voltage that can be carried by a conductor between 2 disimmilar metals causes one to corrode away.

a sacraficial anode allows that material that gives up electrons easier to be destroyed rather than your pricey aluminum parts.

by changing out the coolant, every year, what you have done is remove the contaimantes that allow it to conduct electricity.

While it is true becoming acidic, increases the conductivity of the "water" that in itself is not the reason for the corrosion.

however you have to ask how acidic can it possibly be.
while it isn't truly a closed system, the "water" becomes acidic due to carbon dioxide in the air blending with it to make it carbonic acid.

there are plenty of additives in coolant that prevent this for quite some time.

but it would be interesting if you measured your ph before and after your change.

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as for the in each head comment, it has to do with being in an electrically conductive solution. so they would complete the circuit with "water".

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Well...I did some research...I need to track down a voltage leak...I checked my radiator fluid and I have .422v in the rad fluid. The threshold is .300v I need to find what is causing the leak and check my grounds. I may have to dump the fluid but I want to check the pH level tomorrow. There are apparently "sponges" you attach to the heater core or radiator which pull the electricity from the lining and reduce the loads in the fluid. I called the reseller of the Rad Cap and he said his does the same thing every two years...his other car...looks like the day he installed it 5 years ago...

So now we are on a hunt for a leakage...I am suspecting it is my alternator though. I have a Delco Remy Si10 which is supposed to put out 14.6v when you "turn it on" and I have 15.7v...that over voltage must be bleeding back into the coolant and its holding it.

Don't blast me on the Remy...I had two of them sitting on the shelf and they put out 100amps and were half the price of the Mopar unit 14 yrs ago...internally regulated and "always on" when you revved past 1500rpm.

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as for the in each head comment, it has to do with being in an electrically conductive solution. so they would complete the circuit with "water".

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I did a search on this and I thought I remember reading somewhere that it had to be at the source?

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Grounding the radiator and heater core directly helps. Also rechecking motor to body grounds.

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Radiator is grounded to frame, battery is on the same point. Battery to engine block, starter to subframe, engine block to subframe. The subframe contacts are cables, soldered into large bare terminals and then heat sunk and the exposed bolt attaching it is covered in hot glue to resist oxidation. I was pretty religious about grounds. The only thing I have not done is the heater core, which makes sense now. I can probably add a second heavier cabled ground on my radiator and a smaller flat steelbraid and solder it on to my heater core nipple. I am assuming this voltage spike occurred when I installed my aluminum heads. It's going to get worse now because when I flush my radiator....and my block...I am going to install my Aluminum Mancini Water Pump and housing.