I didn't think aluminium rusted? :dunno:After doing a little research on automobile corrosion I came across the problem of stray currents in the cooling system and how badly it can corrode aluminium radiators. Having replaced my radiator about a month ago because of heavy corrosion I am anxious to check for stray currents.
However, all the instructions on ow to check for this involve sticking the positive probe of a multimeter into the coolant in the radiator and the negative probe onto the battery negative terminal. I cannot see how I can do this with my F.
Can I use the expansion tank and a ground nearby?
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I am not sure about this stray current malarky. 
Currents tend not to be stray, they flow from one source to another, taking the easiest route.
You cannot measure the current in the coolant by placing a probe in the water. This will only give you the potential difference (voltage) with relation to earth. If you put 2 probes in the water, a set distance apart, measured the potential difference and knew the resistivity of the coolant you could calculate the current.
I think what you are worrying about is galvanic corrosion. This is where you have 2 disimilar metals, add an electrolyte (in this case coolant) and you have yourself a nice little electric circuit. Electrons will flow from one metal to another and erode the softer metal. This can be speeded up by the presence of an external electric source.
Really, the only way to stop this is to design it out of the system by insulation, or use of a sacrificial anode to protect the components. As Pete says, the OAT coolant contains corrosion inhibitants to slow the process down anyway, I say slow it down as you will never stop it.
You say you have had one radiator corrode? How old was it?
Aluminium cannot rust as rust is a byproduct of ferous metals.
What is it with all this addition of negative cables and stray currents in coolant? You aren't doing a course in theoretical electrics are you?
Cars have been functioning perfectly well for many years with stray currents, no negative cable and galvanic action. Yes you will get corrosion, but I think you will get an ulcer worrying about these minor problems before your car dissolves.
Currents tend not to be stray, they flow from one source to another, taking the easiest route.
You cannot measure the current in the coolant by placing a probe in the water. This will only give you the potential difference (voltage) with relation to earth. If you put 2 probes in the water, a set distance apart, measured the potential difference and knew the resistivity of the coolant you could calculate the current.
I think what you are worrying about is galvanic corrosion. This is where you have 2 disimilar metals, add an electrolyte (in this case coolant) and you have yourself a nice little electric circuit. Electrons will flow from one metal to another and erode the softer metal. This can be speeded up by the presence of an external electric source.
Really, the only way to stop this is to design it out of the system by insulation, or use of a sacrificial anode to protect the components. As Pete says, the OAT coolant contains corrosion inhibitants to slow the process down anyway, I say slow it down as you will never stop it.
You say you have had one radiator corrode? How old was it?
Aluminium cannot rust as rust is a byproduct of ferous metals.
What is it with all this addition of negative cables and stray currents in coolant? You aren't doing a course in theoretical electrics are you?
Cars have been functioning perfectly well for many years with stray currents, no negative cable and galvanic action. Yes you will get corrosion, but I think you will get an ulcer worrying about these minor problems before your car dissolves.
Sounds like there is a gap in the market on ebay - stray current inhibitor - prototype looks strangely like a tinfoil hat
Correct: But stray current is what the industry calls the problemI am not sure about this stray current malarky.
Currents tend not to be stray, they flow from one source to another, taking the easiest route.
You cannot measure the current in the coolant by placing a probe in the water. This will only give you the potential difference (voltage) with relation to earth. If you put 2 probes in the water, a set distance apart, measured the potential difference and knew the resistivity of the coolant you could calculate the current.
Well we can't insulate the cooling system because the coolant runs through the block and not knowing the full history of the vehicle I do not know what mistakes other people may have made. The designers try to design this out but a mechanic who doesn't realise that an improper earth can rust your rad could easily made the mistake.
Not sure of it's age, could have been the original. But that doesn't mean it was corroding for ten years. And a new rad can corrode through in a matter of weeks if this problem exists.
Cars have a lot more electrical equipment now than many years ago and as already stated, this affects aluminium rads a lot more so than older copper ones. So really, this is a fairly new problem that modern cars suffer from.
Just because corrosion happens doesn't mean we shouldn't try to slow it down. Boat owners take corrosion much more seriously than car owners because to them it is far more serious and can mean the difference between life and death. But surely just because it is not that serious on cars doesn't mean we cannot learn from them.
Earthing cables and stray current protection may not make a huge difference. But isn't that the same for every mod and bonnet stripe? What seems important to one person may not be important to another. Like seat belts 30 years ago!
Sorry if I am annoying people harping on about electrics, but you do have a choice
Thanks Steve. Just what I was looking for. Not sure why I didn't think of it myself.
You're not annoying at all, just me being flippant.Sorry if I am annoying people harping on about electrics, but you do have a choice
I can see your logic, but as an electrician I very much doubt that any actions you take will have anything but a negligeable effect on the system. Correct bonding will limit the anode/cathode will reduce the galvanic effect, but you will never stop it. Corrosion is a force of nature and cannot be stopped.
To be honest you would probably gain more of an advantage by carefully selecting good quality parts, as cheaper materials will corrode quicker.
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