having just posted this as a reply in another existing post, i figured it might be of some interest to some others here and usefull to those with rust issues..

sacrificial anode... or anodic cathodic reaction
most metals want to give up electrons and the process is helped by moisture in the air among other things so rusting is an inevitable consequence of metal ownership..
3 things that help stop rust
1 composition of metal (could explain this as it applies to stainless, but its kinda irrelivant here.
2 coating with a non conductive skin ie paint..Por 15 is as far as i can tell a very flexable coating so it doesnt crack like ordinary paints thus not letting the electrolite (water in the atmosphere) in I assume fish oil does the same (creates a barrier against conductive moisture) moisture is the most common cause but other metal to metal contact will do the same...(ever left a tool on a piece of metal for a while and seen how quick localised rusting takes hold??

3 the sacrificial anode... some metals want to give up more electrons more easily that the metal you want to preserve.. fitting a hump of this to your metal will mean that it is far more likely yo corrode than your metal.. it will also give up electrons to your metal if your metal gives up its own thus replacing any loss..
there are charts available probably from metal suppliers listing the order of metals based on their ease of shedding electrons..

sections of metal that have been stressed or heat damaged are more likely to rust too.
and even though oxygen is vital to rusting a limited suppluy of oxygen makes the rust rate worse (hence worse rust under semi covered areas and under scale, which is the common cause of pitting)... (this may explain why salty moist air is worse than plain moist air as the salt forms a type of shield/skin??
Anyone want to add their knoledge.. i dont claim to be the learned master here,, probably just enough info to have half the story.. im sure there must be some science types out there...you cant all be computer techs surely!!!

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No longer Ms Westwoods mini outside her original kings road shop

Salt is better at rusting things out as the disolved salt provides atoms to transfer the electrons etc. 100% pure water if I remeber correctly does not conduct electricity if you add salt to water it will conduct more and more electricity that's why salt is bad in terms of rusting stuff out.

The sacrificial anode thing basicly I think comes down to bolting a lump of Zinc(most common I think) to your car that's were Zincalume (spelling) comes from this is a zinc like coating on metal sheeting.

Rust needs oxegen so limiting oxegen supply doesn't speed up rust it should slow it down. Stuff like scale etc I think traps moisture against the metal which speeds up the rusting process hence getting rid of all the dirt and crap out of your wheel arches etc helps prevent rust.

There is another way to prevent rust I can't quite remember but it is commonly used to stop jetties rusting and that is you create a small charge in the metal. I can't quite remember but I think it was so that any electrons stripped from the metal are immediately replaced meaning that none of the atoms of metal become positively charged and can be carted away by water molecules.

Um that's all I can remember of High school chemistry for now maybe some of the school kids can tell us more or ask thier teachers

Yes paint, fish oil, galvinising???, all creat a barrier to stop water and oxegen coming in contact with the metal.

The interesting one is Aluminium, Aluminium oxedise with just air so any unpolished aluminium has a very thin oxidized layer giving aluminum it's dullish colour (unpolished the polish forms a protective layer against oxidization) The oxidized layer in aluminium actually stops further oxidization Aluminiun oxide is extremely unreactive and well bonded to the aluminium metal so it can't be carted off by water molecules so aluminium dingies don't rust.

With all the above high school chemistry was a fair while ago so I might be wrong

EDIT:Fixed spelling (well some of it)

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Roads need more corners
A Deluxe(CG13DE), 2 Clubbies(998 and 1275) and 2 Morris 1100Ss

Don't really remember orunderstand the technicalities but it's something along the lines of sending a negative charge over or through the metal surface so it forms an excess field of ions. This protective field prevents the rust and oxidisation process from occurring.

Long time since I went to trade school and many brain cells have diminished but it kind of makes sense!!

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1965 Morris Mini 'Woody' Traveller

yes that is a number 4 a small electrical current that supplies the free electrons..(do they build this system into any cars [ probably not into average jobs, manufacturers want them to rust out quick so you buy a new one])

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No longer Ms Westwoods mini outside her original kings road shop

http://www.ausmini.com/forums/viewtopic.php?p=77620#77620

Theory is all well and good, but has anyone successfully used a sacraficial anode on a car?

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"Life is not like a box of chocolates... it's more like a jar of jalapenos. Whatever you do today, may burn your arse tomorrow."

Is this one of those electronic gizmos you people are talking about?

http://www.couplertec.com.au/

I don't know how well they'd work. Since most cars are negative earth, there is always a current flowing through the body anyway. So this must just sit there and go for the ride.

good question... i can see there point about the tankers etc as they are emersed in the electrolite.. and any sacrificial anode would need to be in conductive contact to the part rusting.. if it was going to have a chance of working i would susspect more small ones would be better than one big one as its not going to be submerged (hopefully)..
maybee this systems reliance on conductivity makes it only practical in water or in extreeme high concentrations of it..(i know my outboard leg has one and it isnt rusting)
still a good repair with thought towards continued use ie the way you are doing yours should last for ages... many many years.. maybee thats as good as the answer gets fix it properly. choose your surface coatings wisely, and keep it as clean and as dry as posible, keep on top of any signs of re apearance......
AND hear ye bog lovers.....dont hide stuff with boggg.....

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No longer Ms Westwoods mini outside her original kings road shop

I guess if any of us had a real answer to the rust question we would:
1. be very wealthy
or
2. be very wealthy because the car companies had bought the idea of us to hide it.
or
2. have been bumped off by one of the car companies for spoiling their aftersales/repair market and not selling them the idea!!!!!

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1965 Morris Mini 'Woody' Traveller

Keep it garaged, clean and don't drive it in the wet...

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Lillee - 1969 Morris Mini K

pffft no fun there!!!! lol

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Potato