sacrifical anodes

[Nick Woods]

Ok, so I'm still rabbiting on about bimetallic corrosion smile.gif

 

From what I've learnt so far, it's possible to use a sacrifical anode to prevent two metals (such as the steel and aluminium used is a seven) from corroding it.

 

Has anyone tried this and if so what metal was used and did it work ?

 

Thanks

 

 

 

 

Nick

P8MRA - The green one with red wings

 

Edited by - Nick Woods on 25 May 2002 19:13:05

[Bob Corb]

This idea has been around for decades and a few dubious sorts have tried to sell it to the car owning public. Unfortunately unlike boats (where this method of corrosion prevention is widely used, ask any canal boat owner) cars are not fully submerged in water (very often!). This means that the elctrical circuit for the sacrificial reaction is not completed and therefore doesn't work.

 

Best sticking to rinsing the car off with clean water and parking in a nice warm dry garage, with the odd application of WD or waxoyl aerosol around the back suspension and down the sides of the footwells etc...

 

Cheers

 

Bob

[Hibster.]

Bob

 

On your advice I now plan to park my car in the canal, after all I've never seen a rusty supermarket trolley in there wink.gif

 

I do have shinier rear wings than you

 

Paul

 

"I had a car like that before the war" confused.gif

[Nick Woods]

Thanks Bob - I'll give this up as a bad idea then. Once I've sorted out the corrosion I do have (which isnt a huge amount) I'll just make sure to drown the thing in Waxoyl and repeat every year.

 

 

Nick

P8MRA - The green one with red wings

[Roger King]

Yes, I've got two ruddy great lumps of magnesium on the hull of my narrowboat as sacrificial anodes - never heard of such a thing on a car though.

[oilyhands]

Yiou can only have a sacraficial anode where you have an all immersing electrolyte.. some Alfas have a magnesium plug screwed in their head waterways to avoid electro-corrosion of the head.

 

Dave

[KayTee]

Hmmm ...

How about a swirl-pot like thing in the return pipe from the engine to the rad, with a 1" thread in the bottom and a magnesium stick plugged-in right there? They use these things in larger heating tanks. These 'sticks' are way too long for car use (8"-10"), but can obviously be cut down.

Would one need to have a 'ground' strap from the aluminium cylinder head to the 'pot' ? I was told so, but the water itself would conduct the current, wouldn't it ?

 

Cheers! - Karsten

[DohNut]

I was inspecting corrosion in the ballast tanks of a supertanker a few weeks ago, The crew had taken extra special care of their anodes - given them a nice new coat of paint *because they were rusty* he proudly announced!

[b)]

 

Nick

[R2D2]

Galvanic Cathodic protection is quite common and works well on structures that are floating or buried.

 

As aluminium is significantly more anodic than steel it will tend to protect the frame at the cost of the body.

 

It would be quite difficult to find a metal that was much more anodic than aluminium that wasn't very reactive.

 

Aluminium is commonly used as sacrificial anodes on ships (zinc and magnesium are used as well.

 

I would think the best answer is paint or coating if possible.