MG
The Classic Marque

Anam, one of the ofentimes cited reasons for the change from positive to negative earth was to reduce electrolytic bodywork rusting with, I think, the car body acting as an anode with positive earth. I could well have that the wrong way round?

I was just wondering if the same effect might be happening with the engine itself being connected to a positive earth early car.

It seems strange that the thermostat housings always seem to be erroded.
Would be interesting to know the composition of the alloy as Zinc is often alloyed in Aluminium to enhance certain properties.

Have seen a brass nut and washer dezincify on a forged bronze bolt to such an extent that it looked like an aero chocolate bar ! not good for a stem bolt on a wooden yacht! Obviously builder...

The answer is probaby in one of these Guy.

https://www.corrosionclinic.com/corrosion_A-Z/polarization.htm

https://www.safe-skipper.com/galvanic-and-electrolytic-corrosion/

But I seem to recall, pos earth is worse than neg earth where electrolosis is involved. But if only chemical, not relevant I think.

Would electrolytic corrosion be influenced by whether it was positive or negative earth car?

I'm inclined to think electrolytic corrosion is involved Richard as well as what Willy said. Never known that much corrosion on a newish part or even an older part in the past and I seem to remember sometimes running with water only in the summer and you put a bit of antifreeze in, maybe 10% the night before the first hard frost was forecast.

Just changed mine last week after many years and low mileage- all looked good - standard Bluecol Blue back in - roughly 50% I guess.

I do wonder if there is also an electrolytic corrosion going on as well with all the dissimilar metals ? And some likely dodgy alloys nowadays. Aluminium being way down on the scale.

On most smaller boat engines there is provided an anode - ok espec...

You've convinced me to change it after 2 years Willy! Maybe I should check the w/pump.

It's the coolant going off that's caused that---I've seen radiator caps, heater taps, metal heater pipes and freeze plugs rotted away after about 4 years-Water pumps seem to survive for some weird reason--longlife coolant is the answer if it's not going to be changed regularly(2 years).
Had a mate with a Dino that was going into storage, normally you'd just drop the coolant out and leave it dr...

Guy
I used softened tap water (about 70%) and standard antifreeze. I was surprised at the corrosion too, never known anything like it (Moss part). I've put it back on, it should last a bit longer hopefully with new coolant - might get some distilled water (never have before).

£54 a bit steep Anam. Maybe I'll just accept the housing is a "sacrificial" part.

Great that you can use your hand Bill. Good news.

Luckily antibiotics aren't addictive. But they screw up your gut with high doses for long prescriptions; so the doctors tell me. Takes a while for gut to settle. But actually, the Flucloxacillin I've been taking, doesn't seem too bad. So hoping when I stop this week, my gut will get back to normal quite quickly. Plus I've been off the tipp...