A science question?

Tourershine

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This is a bit of a random one, but I wanted to work out this issue for my own education.

We had an aluminium built Caravan that a customer wanted his exterior fully Restoring today. The Caravan had all the usual issues we deal with and are very familiar with, like the normal oxidised surfaces. This is all part of what we do, and know these issues very well.

However, this specific Caravan was a 2010 model and owned my the same owner from new. The customer had always stored his Caravan on his driveway in the same position. This position was directly underneath what I can only assume was an electrical cable. The sort you see looping from house to house.
The customer told me it was a copper cable, which I couldn't confirm, but it wasn't insulated, just a bare cable.

Anyway, the issue we had was where rain water had been constantly dripping on the roof of this Caravan and run down the front panel and a small gap in the awning on one of the side panels. What this had done was eaten into the painted surface to such a degree, that it took me hours of very careful machine polishing and wet flatting until I finally removed all the traces of the damage, thankfully without going through the paint. My customer mentioned that his old Caravan had the same issue, but the water had literally eaten through the aluminium.
I've seen a lot of issues with Caravan and Motorhome surfaces, and explained many of these in depth, including being the first company called by manufactures and dealers with surface issues they either cannot rectify or work out what's happened, but this is something i've never come across in all my years of experience.

I wonder if anyone can explain the correlation between the cable, the water and the almost acidic characteristic effects on the paintwork.
 
It's possible if it's a copper cable and has been wet and had salt thrown in somewhere, sea air for example, that the corrosion of the cable could have accelerated the corrosion of the caravan. Copper doesn't rust but does corrode so that will have dropped ion laden drips which could be responsible?
Any chemists/physicists in the house?
 
It's possible if it's a copper cable and has been wet and had salt thrown in somewhere, sea air for example, that the corrosion of the cable could have accelerated the corrosion of the caravan. Copper doesn't rust but does corrode so that will have dropped ion laden drips which could be responsible?
Any chemists/physicists in the house?

No sea air, it was in Coventry.
 
This could be the answer.... black type staining.....

What happens when water reacts with copper?
Copper does not react with water. Copper does not react with water because the oxygen in water is locked into a compound with one part oxygen and two parts hydrogen. Copper oxide is a compound from the two elements copper and oxygen. ... Upon strong heating, it forms a black solid of copper oxide.

but for it to attack aluminium other environmental influences will be involved
 
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When my thatched roof was re thatched I put a bare copper cable in the ridge. Rain runs off the copper, creating a very weak solution containing copper sulphate (CuSo4) and copper carbonate (CuCo3).
Both of these are algicides, known and used to prevent green algae and moss from growing.
Copper Sulphate is used in industry for etching Zinc.
Maybe it etches Aluminium too if a constant drip of a very weak solution of it is dripped on to the Aluminium??
 
This could be the answer.... black type staining.....

What happens when water reacts with copper?
Copper does not react with water. Copper does not react with water because the oxygen in water is locked into a compound with one part oxygen and two parts hydrogen. Copper oxide is a compound from the two elements copper and oxygen. ... Upon strong heating, it forms a black solid of copper oxide.
I follow your thinking and agree, after all, copper pipes are used for plumbing!
But, remember the "acid rain" crisis in the 1980's? It turns out rain isn't just water, it contains various other chemicals, including very weak, sulphuric acid. Hence all the damaged limestone cathedrals!
 
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Apparently after 50 odd years of living in the same house, the electricity board are replacing the cable in the next few days with an insulated cable, hence my customer having his Caravan restored back to it's factory shine.

I was hoping there was an obvious answer to this problem. There has to be a connection between the cable and the water dripping.
I've seen so many different issue with Caravans and Motohomes, baring in mind that they spend far more time sat in one place than a car, but this one perplexed me.
 
As a spin off ....£2000 buys this ....that will protect their vans.

DE47D655-56A0-43DD-B467-AF2FABEF3779.jpeg
 
Having said all that .....the rain we all think is safe is full of other nasties pickup from the pollution we all breath...

But ..always a silver lining...Keeps @Tourershine in a job ....
 
Since the introduction of "low sulphur" and "ultra low sulphur" diesel, farmers now have to spread sulphur on grass, it's an essential trace element for grass. The rain used to provide enough sulphur, now it doesn't!! That proves your point VanDamMan.
 
IMO it’s an acidic reaction on the copper cable by acid rain, low sulphur fuel isn’t no sulphur and there’s a lot more vehicles than there were a decade ago.
If it’s anywhere downwind from a shipping port there maybe a very high level of sulphur in the air.
 
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Just because the caravan was stored in Coventry don't rule out salt in the rain. I'm in Telford and seen what I have always assumed was salt deposits on the van windscreen after we've had serious rain and gales usually from the south west. The marks on the windscreen looked very much the same as those left when parked at the coast.
 
Looking at this from a sparky angle I’ve never seen any cables that are totally uninsulated ?
The only cables I know of that could be uninsulated are the main runs between pylons, and I’m talking about the high voltage stuff that runs down the side of motorways
 
Looking at this from a sparky angle I’ve never seen any cables that are totally uninsulated ?
The only cables I know of that could be uninsulated are the main runs between pylons, and I’m talking about the high voltage stuff that runs down the side of motorways
I grew up in a house with uninsulated cables at the bottom of the garden, they are still not insulated but they cut the trees down that used to grow around them.
 
If you look at roofs of older houses with flashings/soakers around chimneys, you'll often see patches directly below - like this for example :
1596149330763.png

This is due to zinc reacting with the rain, preventing lichen growth. I imagine it's a similar thing with the van.
 
No real definitive answers then, although some interesting responses.

Hopefully as I haven't seen this in my 13 years of running my business, I won't see it again.
 
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