Hot Rods Galvanic Corrosion

A sacrifical anode is mostly used on boats. It attaches to parts of the engine and the zinc anode gets eaten away rather than the engine parts. I don't know boats, but I think you need to change them when they start to wear out. As I originally stated I have one attached to my radiator cap.

 

The ones I use are 1/4 NPT , I find a place to screw them into the cooling system or I have drilled and taped the intake to install one . They work great as designed to .

 

Nitrate free coolant will also help.

 

So, if I don't have one in my system, it eats all the aluminum parts?

 

country of origin has nothing to do with corrosion.

dis-similar metals with a conductive fluid separating them is called a "battery". seriously it's electrochemical corrosion and there are ways to check for it (measuring voltage between a probe in the rad juice and ground, etc)

iron block
br*** thermostat
zinc thermo housing
aluminum radiator

here's a quickie primer: https://en.wikipedia.org/wiki/Galvanic_corrosion

when i was a kid i found a book on "electrochemistry" in the library, it had some version of this chart https://en.wikipedia.org/wiki/Galvanic_series that i used to make (mostly ****py) batteries from. METALA-electrolyte-METALB. that's what you got.

electrochemical corrosion is rarely "zero" but with some metals it's pretty low so when it take 20 years you don't notice or care. iron and br***, for example. (zinc is a component of br***). but add something more reactive -- aluminum! -- and instant problem.

you can put a "sacrificial anode" (zinc block) into the radiator tank. electrically isolate the aluminum radiator.

but yeah it's a PITA.

 

Heres an article on it...

https://www.hotrod.com/articles/keep-your-cool-preventing-radiator-eating-electrolysis/

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sacrificial anode is metal you literally *sacrifice* to the corrosion mechanism. you install a piece of metal you don't care about to get eaten instead of the one you do care about.

in a boat you're fighting AN OCEAN. guess who wins. sacrifices must be made!

in a car, you have a chance of winning, though it might be hard.

being old enough to remember when we usedta (against all good advice) just dump the block and radiator contents, pour in a gallon of the cheapest coolant i could buy, then top off with a garden hose, it took some time to get over the fact that that's just bad practice.

i now flush etc with the hose but do a block (pipe plug) and radiator complete drain, re-fill with DISTILLED water from the drug store, run that a bit, drain and refill AGAIN with DISTILLED water. when i ran antifreeze i buy what i used to sneer at -- pre-mixed/pre-diluted high quality coolant. the deionized water really matters.

the perfectly ordinary minerals in tap water make a great corrosive electrolyte, especially when you heat it up.

 

Galvanic corrosion or dissimilar metal corrosion does not necessarily need an electrical current to causebthrbcorrosion. There is an anodic/cathodic chart to help decide which metals are compatible. The further away from each other on the chart, the more likely corrosion will start. Case in point, ***anium is very high on the anodic scale it can be destroyed literally by drawing or marking on it with a simple pencil. The carbon in the pencil will attack the ***anium and eventually eat right through it. We would inspect aircraft skin for damage and use a pencil to mark the areas that needed repair. When we moved to ***anium, we wrenches no longer allowed pencils on the aircraft because of the instant and serious damages carbon would do. Likewise carbon fiber compositesnare never installed where they can contact ***anium. All metals are listed on that chart and will react by eating or being eaten by another metal if not properly matched. Ad electrical current and the process speeds up. I taught corrosion control for several years in the military and with some of the aircraft manufacturers I worked for. Teaching it was sometimes as exciting as watching paint dry but at the same vitally important. W lost a couple of B-52s and two crews because of corrosion, tropical humidity, and stress in July of 1969. Agterbthat, we all took corrosion control much more seriously. So closely match anodic/cathodic properties, limit exposure to electrical current flow and humidity. It may not eliminate galvanic corrosion but it will give the metals you are using a much longer life.

 

This will explain it in detail: https://performancemetals.com/pages/sacrificial-anodes-faqs How to test for it.

 

Galvanic anode.

I use a quality anti-freeze mix and contemplating using a pencil sacrificial anode in bottom of radiator. A quality thermostat housing makes a difference as well. My DD suffered from stray current causing the plastic/alloy radiator to corrode.

 

Check your radiator for small voltage. Earth leakage to the cooling system is usually the cause of your problem. Your t-housing is acting as a sacrificial anode. Also regular coolant changing will help. 3-5 years tops regardless of what the manufacturer says IMO.
Cheers Mark.


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Electrolysis is what I have always understood it to be.
When designing houses we were always aware of using dissimilar metals from roofing material to guttering/spouting, downpipes etc, - no electrical current involved.
tomic, in post 35 gives the best description as I was taught.

 

Thanks for all the links guys. I'm all ears! I did read (or watch) everyone you gave me and I'm more confused now than before. I didn't know you had to have a masters degree in electro-chemical engineering just to add coolant to your radiator!

No, on a more serious note, this has been a re-occurring problem with this car and I really don't know how to fix it. So I just keep replacing parts and have fun driving it.

I have your typical iron block (SBC) with aluminum heads, aluminum intake, hi-flow aluminum water pump, aluminum radiator and a br*** heater core, in a gl*** car with grounds everywhere.

I end up changing the coolant every 2-3 years, because I've lost 2 or 3 chrome aluminum (or pot metal) thermostat housings. I even had a thermostat rust through one time, to where it wouldn't heat up. I use a mechanical temp unit.

I think I'm doing all the right things, but I am a little concerned about the heads and intake though.
I use distilled water (which is highly acidic, by the way), in a 50-50 mix of antifreeze (which makes it run 5* hotter than plain tap water) and I've come to the conclusion, WE'RE ALL GONNA DIE!