They make additives to control that, Modern antifreeze will stop it too. Y blockers that had the dual quad setups in '56 and '57 E codes had the problem with the intake. The alloy and heat treat that John will use is going to be much better at resisting the corrosion than what was available 50 years ago. Have not had any problem with the aluminum Water pumps or Timing covers..........YET! Just about every car on the road  any more has aluminum and iron castings together.    

thats good to know maybe john could teach the japs this or maybe geelong water is too hard  our alloy heads are always causing problems one of (& this is sacralidge) our ford 6 cyl heads used to grow 1/2 an inch

         You're right about the hard water, too much iron in the water acts like a conducter, Sulpher's no help either.  

Using aluminum intakes back in the '70s and working in the aircraft industry taught me a bit about electrolysis, so I started using distilled water in the rad & the battery.  The distillation process takes all of the minerals out of the water, so It extends battery life and cuts corrosion of cooling system parts to nil. 

Thanks for bringing that up.  I was going to mention it, but decided to let it rest.  Now it's awake.

Where I worked, we had electronic high frequency induction heaters to heat billets before upsetting or extruding them.  We used deionized (not quite the same as distilled) water to cool them, and was told by the manufacturers of the heaters not to use pure deionized, it was too aggressive and would dissolve copper and aluminum from the cooling systems.  We mixed deionized and tap water, and used an ohm meter with the leads an inch apart in a cup of the water, was looking for between 100,000 and 150,000 ohms.  More than that, too aggressive, less than that, to much conductivity which killed the efficiency of the heater.  Bled too much power to ground through the water, even though we had rubber hose connections between the heart of the heater and the heat exchanger, which was connected to ground.  We couldn't even use black water hoses because the carbon content of the rubber made them conductive.  These units operated at 3,000 or 10,000 cycles per second depending on model, so I didn't know if the aggressive water problem was similar to a car's cooling system or not.

John in Selma, IN

Tap water usually has desolved minerals - therefore is it "acid" or "base"? The mixing instructions John was talking about are a practical way to correct an imbalalnce.

Would the best descrioption be that we want the coolant to be "neutral" when all is mixed together? Could this be checked with something like the pH meter my wife uses for her garden soil? 

"Extensive testing has shown that a coolant pH below 8.3 is not acceptable for use in engines due to its corrosive nature. The correct pH value should be maintained between 9.5 and 10.0 pH. Below 9.0 pH it is advisable to flush the cooling system and refill with a new coolant solution"

A pH of 7.0 is exactly neutral - this amount described is a "base" solution and the scale goes up to 14.0 max. Fluid pH below 7.0 is considered "acidic" and 1.0 is max.

Guess I ought to find a new "instrument " for my garage - my 312 is full of distilled water (cheap at Walmart) with a bottle of Prestone anti-rust additive package only. I don't have a clue what the pH is .....but it sounds like it might be a good idea to know. Just a guess - I'd say the water is 7.0 and the additive package turns it "base" - but it may need more than one bottle to get up to the range described. the stuff made my radiator water look abit "milky"......

"Water Quality is extremely important if make-up water is added, or if coolant is diluted. Major engine makers recommend the following coolant make-up water specifications:

• Hardness (calcium), less than 170 ppm
• Chlorides, less than 40 ppm
• Sulfates, less than 100ppm
• pH neutral

Water exceeding any of the above specifications should not be used. Use distilled water, de-ionized water, or equivalent."

also:

"Glycol: Engine manufacturers recommend coolant composed of 50/50 water/glycol solutions providing enhanced freeze and boil protection. An operating range of 40% to 60% antifreeze (glycol) is acceptable. Use of glycol percentages exceeding 65% may cause SCA dropout, waterpump seal leakage (!) and engine overheating."

and:

"pH:Coolant pH values have a "normal" range of 8.5 -10.5 when precharged with nitrite/nitrate or nitrite-molybdate SCA." ----(SCA is "Supplemental Coolant Additive")

"When pH is (found) less than 8.0, coolant should be drained and flushed."

"Coolant pH exceeding 11.5 will corrode aluminum and promote scaling"

Immersing the strips in the coolant sample (at less than 110°F) causes three bands on the strip to change color. The three stipes are (1)  Nitrite ppm (2) Freeze point °F (3) pH 

It also warns that these strips ar not for use with Texaco Longlife Coolant or Dexcool

I may need to "test" the warehouse forklift........

"Chlorine/Chloride content: Antifreeze rapidly degrades if chlorine or chlorides are present in the antifreeze. Chlorides in the presence of acid components are especially corrosive towards aluminum radiators. Chloride is also corrosive towards copper and other metals. Chlorine content (determined by ASTM D-5384) in the coolant is the first thing a warranty claim will look at."

"The chlorine/chloride test is to determine the quality of unused coolant (?) as well as whether the user is taking proper care of his coolant and keeping it under 250 ppm of chlorine (an OEM requirement). Adding distilled water to coolant minimizes chloride content. Note tap water often contains about 500 ppm of chlorine."

I got a bottle of the test strips and dipped one in the radiator of the "green" (ahem) forklift.... It was previously flushed numerous times (with straight tap water), and then completely filled with distilled water and a single Prestone additive package (should have kept the bottle). No antifreeze (this is Arizona).

The NAPA test strip showed: Nitrite 500/800 ppm / Freeze point 32°F / pH 7.0 - which is of interest simply because it looks like you can get the Nitrites package by simply shopping for a yellow plastic bottle at Walmart or the auto parts store. Takes two for my size of cooling system though because the NAPA bottle says 1200 ppm is ideal and I'm only half way there. The strip shows the distilled water plain enough - neutral pH and no freeze resistance.

This is just making me ask more questions. Now I'm wondering if the recommended 50% antifreeze solution is necessary to make the mixture "base" enough to get the pH up to the 8.5 recommended minimum and beyond. I was hoping to not use antifreeze at all as it makes life pretty simple when doing a regular flush of the system. I think I'd like to just use distilled water, an additive package, and adjust the pH with something else.

Found other web references to the pH of radiator coolant late last eve - one stated that the "coolant should be a mixture of distilled water (pH 7.0/7.2) and a glycol based antifreeze (pH 10.5). With a 50/50 mix this nets an unadjusted pH value of approximately 8.75. This is low as the optimum value should be in the neighborhood of 9.2/10.2 ......." and after this grand revelation, they never suggested any method (or chemical components) of "adjusting " the mixture. I think we need to know what this adjusting chemical is - ideas or personal knowledge anyone???

Later I found some comments about a simple concoction used specifically for an aluminum headed small chebbie: 5% distilled water and 95% antifreeze - with interesting reasoning applied. First - the aluminum heads are much more efficient at transfer of heat and can successfully be used with the nearly straight antifreeze - whose molecules don't absorb heat as well as water. Second - the concoction has just about exactly the right optimum pH to avoid corrosion difficulties. This set-up will protect the heads and aluminum parts OK I'm sure - but freezing might be a different issue as straight antifreeze isn't as good at low temp protection as a water mix.

     A ph of 7 or 7.2 is basically neutral. That's what I would shoot for. Are you confusing acidity or Alkalinity with electrolysis? I'm pretty certain if we simply follow the recomendations of the newer Aluminum headed vehicles we'll have no problems. I would suggest a rust inhibitor be used on your 50 year old cast iron block after it's flushed thoroughly. 

Nearly all of the coolant tech specs you can find are based on the required protection of diesel engines in fleet vehicles. The items they are trying to protect are exactly the same as we wish to protect in our gas engines. Iron blocks - pump seals - aluminum housings - copper or aluminum radiators ...... They never mention electolysis - only control of solution pH.

Virtually every tech source I found recommended that the finished coolant package be alkaline - not neutral. In fact, the numbers were pH on the order of 9.5 to as much as 10.5. This would make the solution somewhat naturally resistant to low level electrolysis correct?

Every tech source also recommended the use of distilled water (pH 7.0/7.2) to minmize the entrance of any extraneous elements that produce scale and also "start" the solution at neutral pH.

The use of tap water (with chlorine) was discouraged because it interacts with glycol antifreeze and becomes acidic (creates chloride compounds). It also contains solution elements that leave scale.

50/50 was the preferred mixture of antifreeze to water - but glycol antifreeze apparently has a pH of 10.5. When used at this ratio with distilled water the pH of the solution only reaches 8.75 - not up to the recommended 9.5/10.5. I don't have a chart at hand but 50/50 might not completely do the trick in wintertime Canada (lower than -34°F). 

Nitrite/nitrate additive packages were recommended - the NAPA coolant test strips showed 1200 ppm as a preferred level. This additive apparently resists rusting of iron in particular when subjected to high doses of sonic vibration.  

My bird has its cooling system filled with distilled water and a Prestone additive (no antifreeze) ph is 7.0 - just as you were thinking - so was I. But the testing kit I bought from NAPA indicates that the nitrate level is low (by about 50%) and the pH is low as well. A second bottle of the additive will probably fix the nitrate level OK - but what can be used to raise the pH of the solution? (short of going to an antifreeze mixture). 

after i posted i remembered acid rain something we dont think a lot about here but we do get it every now & then.

        I'm sure the pH levels were concocted based on the use of some form of anti-freeze. I don't run anti-freeze in the F code car, it never goes out when the temp is much below 40. Also race tracks have a dim view of Glycol on their racing surfaces. I had not thought about the relationship of pH to conductivity, somebody will have to explain that to me. This conversation started out based on electrolysis, and wound up discussing erosion from acidic or alkaline based coolant. You may be on to something, but I'm not sure what. Aluminum does not like alkaline contact, but it absolutely hates acidic conditions. Maybe much of what we THINK is electrolysis is actually deterioration from reactions to the coolant. To me it makes no sense to run a pH that alkaline with either cast or aluminum, I'm going to ask some people some questions and see if I can come up with an answer.  

Using a radiator cap with a sacrificial anode would give you a visual indication that something was up. But erosion of the anode would also indicate that you need to do something - not just change the cap.

One tech source suggested use of a digital volt meter to test for "electrolysis" conditions. Suggested: run engine to temp with radiator cap off. With the negative probe on the lowest ground (battery post in most cases) and the positive probe immersed in the hot radiator fluid (not touching anything but fluid), check for DC voltage. If the voltage is as high as .3 vdc  - it suggested draining, flushing and refilling with new coolant. Which usually would cause the coolant solution to go to neutral pH (distilled water for instance) or above (to 10.5) for pure antifreeze.