Naked Science Forum

Non Life Sciences => Technology => Topic started by: Mazurka on 16/03/2010 20:58:33

Title: Could cathodic protection by applied to a car?
Post by: Mazurka on 16/03/2010 20:58:33

I am about to buy an old camper van, which as well as many clever well designed bits comes with free rust (bargain).
Whilst I can treat and repaint the obvious spots on the bodywork, could I in some way rig up cathodic protection for the bits I cannot easily get to (i.e. the underside and chassis)?
If so, how would I test its effectiveness (and driving into the sea is not an option)?
and are their any hidden dangers in this approach (or put another way why is it not commonly done)? 

Title: Could cathodic protection by applied to a car?
Post by: Geezer on 16/03/2010 21:32:15

Unless you kept it immersed in water, I'm not sure it would work. However, as I'm sure you are aware, that could make things even worse  [;D]

I have a vague recollection that a while back they switched the polarity of car batteries from positive to negative earth (which, of course, is really positive - but let's not get into that here) to reduce corrosion. Would that make any sense?

BTW, if it's a VW with the water cooled version of the engine, expect it to drip anti-freeze from the cylinder heads.

Title: Could cathodic protection by applied to a car?
Post by: Mazurka on 18/03/2010 09:45:08

Hmm, whilst I know it was developed to protect ships, it is mainly used to protect iron bridges and buried pipes - and whilst pipes are in a moist soil (which I suppose forms the electrolyte for the cell) it is moisture that causes rust, so i am not yet conviced it would not work.

No, its a renault traffic, so hopefully I will spend less time waiting for the breakdown service than with a VW...

Title: Could cathodic protection by applied to a car?
Post by: graham.d on 18/03/2010 12:42:37

For boats in saltwater it is normal to add a piece of zinc (electrically connected to the boat's ground) somewhere not too far from the propeller. (I'm not sure what they do on big ships which are all metal). The zinc is a sacrificial anode that preferentially gets etched away rather than the rather expensive bronze propeller. If it is getting etched away it's doing its job. I'm not sure if this would work on a car because it is not immersed in an electrolyte (at least not deliberately) so there will be lots of disconnected individual "circuits" where there are unconnected patches of wetness.

Title: Could cathodic protection by applied to a car?
Post by: Mazurka on 18/03/2010 16:50:47

Ok, I am practically convinced, although remian intrigued as to how it works to help bridges.

Title: Could cathodic protection by applied to a car?
Post by: vittorio on 02/05/2010 08:59:24

cathodic protection works only if there is an electrolite that carries current between the galvanic anodes and the item to be protected. you can find someone on the net stating that is possible to protect car with something similar to cathodic protection but is not true.
the only methods to protect a car from rusting is a good paint.

Mod edit - Link removed.  Please don't spam your site here.

Vittorio