Sacrificial Anode
 

One weakness in our Wankle engines is deterioration of surface metal leading to dreaded water jacket failure.

A friend of mine introduced me to the concept of introducing a Sacrificial Anode to the cooling system to help extend engine life. So I fashioned a plug and play Zinc Anode that directly replaced the block drain plug and installed in the engines in concert with two separate project cars. If anyone is interested, I can make some more and sell them for $30 shipped. But becoming a quasi-Vendor isn't the point of this thread.

At issue, I won't know just how helpful they are until I replace one of those engines which hopefully won't be for a long time.

Noted that some of the most experienced Wankleheads wonder this forum with many even holding Engineering Degrees. So I thought I'd reach out and ask if anyone has gone full cycle using a Sacrificial Anode and can testify as to their benefit. Or, what others think about making installing one of these standard procedure for go forward engine rebuilds?

Cut and paste from one web site:

"When metal surfaces come into contact with electrolytes, they undergo an electrochemical reaction known as corrosion. Corrosion is the process of returning a metal to its natural state as an ore and in this process, causing the metal to disintegrate and its structure to grow weak. These metal surfaces are used all around us -- from pipelines to buildings to ships. It is important to ensure that these metals last as long as they can and thus necessitates what is known as cathode protection.

Sacrificial anodes are among several forms of cathode protection. Other forms of cathode protection are plating, galvanization, and the formation of alloys.

What materials are used for sacrificial anodes?

The materials used for sacrificial anodes are either relatively pure active metals, such as zinc or magnesium, or are magnesium or aluminum alloys that have been specifically developed for use as sacrificial anodes. In applications where the anodes are buried, a special backfill material surrounds the anode in order to insure that the anode will produce the desired output.

Since the sacrificial anode works by introducing another metal surface with a more negative electronegative and much more anodic surface. The current will flow from the newly introduced anode and the protected metal becomes cathodic creating a galvanic cell. The oxidation reactions are transferred from the metal surface to the galvanic anode and will be sacrificed in favor of the protected metal structure.

Atkins has had those for years.

also that definition is kinda lacking.

electrochemical process is due to the creation of a cell between two points. One side is oxidized (the anode), as it gives up electrons (and losses mass since atoms are ionized into solution) which then reduce a different spot (the cathode) where material from solution builds up. Use of an a sacrificial anode ground into the block (cant be in plastic) essentially changes what the anode is in the voltaic cell. It can still form between two points on a surface as well which is how rust forms as Fe forms a cell with itself.

weirdly, my expresso maker has this problem.

it would probably help to some degree but in most cases the damage has already been done, in other areas such as the excessively hot spots at the plugs and exhaust the anode wouldn't be effective as those heat sources and reactions are localized.

nothing really beats doing proper cooling system services bi-annually.

pretty commonplace in the marine world in both the fresh and raw water cooling systems. They disappear really quickly.

It's an ongoing debate...

You can minimize this by 1) keeping the "electrolyte" serviced. and 2) keep electrical potential to a minimum.
#1 has already been talked about...
#2 you can check resistance at potential areas, and the addition of grounds (wires) can help here.

I don't believe this is a big problem unless you don't change and flush your coolant at proper interviews - this should be covered with proper maintenance.
Blowby from combustion drops the pH levels in your coolant...
Acidic pH increases the chances of galvanic corrosion.
If your radiator starts to develop pin-hole leaks all of a sudden - this is usually the most obvious problem - then these sacrificial anodes might be a waste of money.

KISS...


-Ted

GREAT STUFF! Thanks.

I checked their web site and all they offer is for their Oil and Water heat exchangers they sell for Marine applications. Nothing that mounts into the block. That said, it looks like what they sell is just an adapter away from working like the ones I made. Also, reference the "angry stig" comment, I made mine so replacement Zinc rods could be simply screwed in to the adaptor plug I made.

Ted,

So you're suggesting besides good coolant maintenance an additional consideration to deal with electrolysis is to mount additional grounding wires? Interesting.

the radiator for example is isolated from the chassis(the stock radiator is mounted on rubber isolators, most aftermarket radiators are solidly mounted) so that the engine acts as the anode. you could reverse this but the radiator will look like swiss cheese in no time if the electrolyte levels rise enough.

so if you want the least material breakdown in the engine you could install an anode into the engine and ground the radiator, if you don't mind possibly needing to replace it.

Ben,

If I have to decide between the life of a radiator and life of an engine, my wallet says that's an easy choice. Since my Koyo uses the stock mounting brackets, thus retain the rubber isolators, then grounding those brackets would be a consideration. Got it.

I'm also interested in Ted's observation about adding additional ground wires to the block. You mentioned that the key points of electrolysis stress is at the excessively hot spots like near the plugs and exhaust. So adding additional grounds wires to the rotor housings is something to consider as well?

That is correct.

Which opens up another can of worms...
Coolants and buffering.
Some coolants will tout "buffering" or "buffering agents".
This is to protect pH.
I believe the "Mercedes type" of coolant does this, and I tout this product as recommended for my customers.


-Ted

and also avoid tap water.

use deionized water if you can get it. Or distilled is better than regular water.

Also, radiators are quite thin, they can fall apart quick.

Distilled is OK.
I do NOT recommend deionized water.
This goes into buffering also.
Since the definition of deionized water is pure H20 with nothing else in it, this causes a negative potential.
Because of no buffer, any ions / minerals / etc. that it comes into contact with will cause it to leach into it.
Deionized water can literally suck ions out of the atmosphere.
This can create potential problems.

Anyone who takes care of aquariums should be aware of this too.


-Ted

I have changed thousands of pounds of zinc anodes in my previous career in the navy. Lots of fun

actually chemically its as neutral as it gets since it has no ions in it. The coolant you is the buffering agent. Ions dissolve based on solubility and saturation of the compound being dissolved. The pH just reflects how much H3O+ there is in solution and having no idea whats in the other water sources, there can be ions causing it to be too basic or too acidic so its best to have a happy medium. Hence why we used deionized water for everything in the lab including the cells I made in school. Ions arent all created equal.

Biologically speaking deionized water lacks any nutrients which is a whole other issue.

A anode will only allow the process to chew away at that material but the material does not just simply disappear it just gets moved to another area in the coolant system.
The best way is to buy Nitrate additive from the auto parts store. Nitrate can be tested with test strips purchased from the auto store (napa) also. Nitrate basically coats all the internal parts and protects the internals from being eaten by electrolysis by basically creating a shield to be eaten instead of the internal metals themselves. Since nitrate is a chemical compund there is no worry about materials being shifted around. Some say use distilled water yada yada but it really does not matter. What matters is the nitrate levels.
I have personally tested 5 different brands of brand new coolants that I had in my garage all brand new never been open and only 2 of the 5 had nitrate in them and it was to my surprise the cheaper brands.

A sacrificial Anode is not the answer. Yes its better than letting your motor get trashed but just band aid. Nitrate is simple and easy and it belongs in the coolant system.
Hope this helps anyone.

From my experiences in the piping industry, the purer the water, the faster the corrosion of the metal pipe it is carried in.

That makes sense. The pure water doesn't have anything for the reaction to eat at so it goes straight for the metal.

Hmm... good food for thought :) I've learned my 1 thing for today!! :lol:

Have you had before and after proof? Inspection of internals of an Engine run on higher concentration of Nitrate vs not? Not challenging, just curious how it compares in actual experience.

Thanks

Which is why you pickle the system