I have recently installed an aluminium radiator in my !50, it has been suggested that a anode may be beneficial in controlling electrolysis in both the radiator and head. Also the water used in the cooling system, combined with anti freeze inhibitor has opposing viewpoints from additive manufacturers. What is the best chemical composition of water that is to be used in our cars?
Do we have some Chemical Engineers among us?
Regards to all.
John.
The XK heads are also aluminium, so nothing really changed.
All modern ready to use cooling liquid will not react to aluminium.
I would say never use plain water, it will eat the aluminium. ( with or without additive )
Regards,
Peter Jan
āPlain waterā ? meaning tap water, right? ā or water without antifreeze or other additive?
I donāt qualify as a Chemical Engineer, but that has never stopped me from expressing an opinion before. 
Use a modern, commercially available, off the shelf, antifreeze solution with the standard package of corrosion inhibitors and find something else to worry about. Unless you are immersing the car in salt water, you donāt need to worry with sacrificial anodes. I am a retired PE, Mechanical Engineer who spent his career in chemical plants. We didnāt bother to put sacrificial anodes on aluminum chemical storage tanks and they lasted 30 years.
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I was hoping you at least stayed at a Holiday Inn Express ā¦
However, you bring good news. I was unable to find a sacrificial anode that would work with my radiator.
Hi Mike, Thanks for your reply.
My quest for information regarding anodes and coolant water is because of the conflicting information that is out there both from coolant manufactures and other sources. The radiator manufacturer that made my aluminium radiator is adamant to use distilled water only to mix with the coolant additive, they also make a serious mention to confirm that there is less than 50mV current present in the coolant at all times to eliminate electrolysis in the radiator.
I have installed a 1/4 npt zinc anode in the top tank to monitor any degradation . Glass lined steel hot water heaters have anodes to prevent electrolysis occurring within the normal warranty period, once the anode in the heater is expended then it is subject to corrosion of the steel cylinder.
Some coolant manufacturers recommend against using distilled water or de-ionized water as to its corrosive properties, softened water or their own water based product being preferred.
Confusing information out there so I was hoping on some Scientific clarity.
You can purchase antifreeze pre-diluted by the manufacturer, eliminating any need to worry about what to dilute it with. The engine is full of aluminum parts, the cylinder head and the intake manifold, as example. Corrosion occurs in these items in the places where they are in mechanical contact in the presence of an electrolyte. If you keep the system filled with a corrosion inhibiting antifreeze solution, you have eliminated the electrolyte. I would note that if the corrosion inhibitors were not effective, no OEM auto manufacturer would spend a dime to use the stuff.
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i would suggest removing the zinc anode from the system as it is just one more metal with a different potential. but i am not a chemical engineer.
Since aluminum has a higher potential than zinc, the aluminum will preferentially corrode over the zinc. Absolutely remove the zinc. If one wanted to add a sacrificial anode, magnesium would be the choice
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Thanks for your interest, we must be reading different information, I have it that zinc is above aluminium in corrosion potential and magnesium is greater again than zinc. Magnesium would corrode faster if used so zinc is preferred as the anode. 1/4 NPT thread anodes are available to the automotive industry and have I been told that the Hot Rod people use these anodes for protection in the engines and aluminium radiators.
John
Hi John, yes I see where you are coming from but that is the reason to have an anode that will sacrifice to save corrosion from a less potential metal. If you are not attentive to the coolant in your car and check is effectiveness for corrosion potential than the anode could be a backstop position, it does not take much to remove the anode to check and see what corrosion has occurred. You do not get a second chance with al. radiators, if it corrodes its normally a throwaway item, many garages have modern al. radiators sitting on their scrap heap.I also have an inline filter on the top radiator hose to catch any foreign particles that may dislodge, donāt want them getting stuck in the radiator.
John
Here is a chart of electric potential of a number of metals. If you look towards the bottom Youāll see that iron (Fe) has a potential of -.44 Volts. It is more noble, ( or considered less reactive) Below that in the chart, is zinc (zn) at -.76 v, it protects the iron above it from oxidation (higher reducing potential), Thus itās use as a sacrificial anode in water heaters, buried propane tanks etc. but it has a lower (-) potential than aluminum. Thus it cannot protect the aluminum at -1.66 v. Magnesium at -2.36 is really the only logical choice to protect aluminum as the others lower down the chart, lithium, calcium, sodium, become too chemically reactive to use.
One might question then why does iron rust so easily by itself. That has to do with the characteristics of the oxide. Iron oxide cracks and shrinks as it is formed, allowing new surface to be exposed. Zinc and aluminum oxides do not and continue to protect the surface from further exposure to oxygen.
Hi Mike, no arguments with that but is conditional that the antifreeze is still within its designed specifications. I have been reading a research paper on corrosion in vintage Lancias and it was stated that once antifreeeze has boiled it loses its effectiveness and should be replaced. How many XKās have had boiled coolant that may now be not protecting their engines. If I can obtain permission to pass on the research I will put up the relevant contact address.
John
Hi Larry, I was right we are reading different tables!! I have a chart of corrosion potential(volts DC ref.Ag/AgCl) that puts Aluminium alloys at between -0.8ā1.0 and Zinc between -1.0 to -2.0. Your explanation of steel corrosion can be protected with zinc and aluminium as per āzincalumeā metal roof sheeting.
Thanks for your input, a friend had a magnesium anode in his coolant but found the amount of erosion to be high, as you would expect from both our charts.
John
This seems to be good info, with links to real world expertise and science.
http://www.sancarlosradiator.com/VoltageDrop/anode_data.htm
Me? I just refresh the coolant once a year. Never an issue.
Iāll take cover behind my barricade before typing this, but when I finally get around to rebuilding and reinstalling my 140ās engine I intend to run it with Evans coolant, which is neat propylene glycol. I know this invites all sorts of āsnake-oilā comments on forums, but I have used it in all my classics for over 20 years and never had any issues. I run zero pressure systems and get no boiling over. And - the reason I chose it in the first place - zero corrosion.
I should add - I have never felt the need to add anodes to any cooling system, whatever itās filled with. The only corrosion issues I have ever had used to be rust and scale build-up in water passages and radiators.
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Thanks Roger, that has given me some more reading to do in this time of Covid-19 self imposed isolation.Personal experience is the best to go by. May be a dumb question but how do you run a āzeroā pressure system,do you have an overflow tank?
I checked out the distribution network in Australia and Evans products are not easily available, closest distributor to me is 3hr drive both ways, I know freight could be organised if I needed any. One point of interest to me was an Agent in a small country town who is very well known as a specialist diesel mechanic and has taken on some of the major SUV manufactures over some inherent problems associated with their vehicles. To have that business prepared to put their name behind the product ,to me, speaks more of the qualities than any of the sales talk.
John
Hi Paul, more reading for me although I think I may of visited this site some time back. One thing that I constantly pick up on is the recommended water that various coolant manufacturers specify to use if you are mixing your own . I am currently using a āPenriteā coolant 50/50 mix and they do state to use ādemineralisedā water with their product. I donāt get that there can be opposite opinions with chemically the same or similar products.
John
Hi John,
If you google it and read the internet comments generally you will find a very polarized set of views! All I can say is that Iāve used it in all my classics, including the 289 Cobra which still his its original (and extremely marginal) cooling system. 4-5 years ago this coped with a few days climbing the Picos range in Northern Spain in an ambient of nearly 40ĖC - the temp gauge broke, but the engine chuntered on beautifully.
Yes, I fit a simple recovery tank (single hose to the base of the tank from the rad cap overflow, single seal cap - doesnāt matter how high the tank is mounted) so that expanded hot coolant is automatically sucked back as it cools. If I canāt buy a zero-rated cap, I simply remove the spring in a normal one.
Roger, I had a read of the safety warnings etc on the back of the coolant container, could be pretty scary stuff and I can see the various opinions about its use without looking at Google. Do you need to have any warning stickers on or around the radiator in case of a road accident or coolant leak? Donāt think it is for me although I can see advantages in using it. Where I live a high summer temp is up to 46*c, the XK stays in the garage then and the Subaru comes out, luckily that temp is rare but we do limit our summer use as it is just too hot in a XK.
Regards
John