Cylinder block corrosion

[davidwheeler]

Following the terrible tales from Australia about their blocks corroding away I have thought to apply a little chemistry.  Hands up those who remember the electromotive series or standard electrical potential as it seems to bee called now.  Essentially, a more negative potential metal will corrode sacrificially when in contact with a less negative metal.  Thus, iron (-0.44) is protected by magnesium (-2.372) OR ZINC (-0.76).   

[davidwheeler]

Oops. hit the wrong key there. To continue..
To clarify, the standard electrode potential has the opposite polarity to the electromotive series.  S.E.P. is used here.
Aluminium is fairly electronegative but should be protected by barium (-2.9), calcium (-2.87) or magnesium (-2.37).  There are more electronegative metals but they are highly reactive (sodium and water anyone?)  Kim told me at the Sliding Pillar that their water was full of iron which would rapidly corrode the aluminium.  British hard water should be protective but blocks the radiator.

So, should we try fitting sacrificial anodes to our blocks?   Barium forms an insoluble oxide coating and calcium is rather reactive but magnesium is not very soluble in water and is used as a sacrificial anode on underground steel pipelines.  It used to be freely available for the Magnesium Flare for ancient photographers but is also used in castings (would anyone like to sacrifice a magnesium road wheel?).  Also, someone must be able to get hold of one of those anodes.  In bulk it is difficult to ignite (but be careful if machining it!)  and is perfectly safe once immersed.

Does anyone think this is worth pursuing or know of a source of magnesium metal?

http://www.answers.com/topic/galvanic-anode

http://www.answers.com/topic/standard-electrode-potential-data-page

David

[thecolonel]

Here you go:

http://www.buymagnesiumanodes.com/magnesium_anodes_uk_suppliers.html

used to export small, and I mean small, lots of magnesium ribbon years ago
the packaging weighed 25 kg the ribbon only 500g, mind you the haz stickers
added a fair amount as well.

Geoff

[davidwheeler]

I am beginning to think it may be too late, I am having terrible trouble with slowly collapsing block faces and am starting to think in terms of new blocks.   The Aussies made a number some years ago, any chance of a new batch?   Alternatively, what have other members done to fill up the various holes and declevities?

[davidwheeler]

I have just fitted a magnesium anode to Sheila's block.  The anode came from http://www.mgduff.co.uk/ .  Fitting is with a couple of stainless screws.  The anodes are provided with threaded holes but with a curious thread so I simply threaded 4mm screws through and used nuts.  Magnesium is tricky stuff, liable to catch fire catastrophically if cut or machined!

[davidwheeler]

5 years on and I come to look at them again - and they have almost entirely disappeared!   I guess that represents a lot of aluminium not corroded away.  I shall fit new ones forthwith.

[simonandjuliet]

Fascinating - be interested to see what my Aprilia block is like later in the year because the Aussies have talked about that these as well

Do you use special water/antifreeze mix as well ?

[davidwheeler]

I use 50/50 water and red antifreeze as used in modern all aluminium engines - but the photo tells it all!    That used to be a suvstantial block of magnesium!

[davidwheeler]

The anode in Sheila was even worse, just a thin sliver.  I researched again and found that the cheapest way is to buy a 1Kg anode from https://www.limekilnchandlers.co.uk/index.php?_a=product&product_id=428    for £24  (50g anodes may cost up to £8!) and cut a 4cm slice (carefully, by hand, with a dry powder extinguisher to hand.  Do not under any circumstances use a cutting disc or try to extinguish the fire with water  - Mg+ 2H2O=Mg(OH)2+H2 but only at 600C plus).    I hope this one will last a few more years.

[Jaydub]

Hi David, If I could throw in my two pennorth, I would advise you NOT to use modern red Long Life antifreeze in older engines as it contains Acid Organic Technology. It is produced as a long life medium for modern engines, but the acid in it will damage the solder in older radiators and can also damage any silicon seals used in water pumps etc. I have been involved in classic cars for a number of years and we only use it in race cars that have frequent coolant changes. Modern vehicles generally have plastic and aluminium radiators, so they are okay. Hope you don`t mind the advice.

[davidwheeler]

Not at all, what would you reccommend please, the old Blue stuff?

[Jaydub]

Hi David, yes you need to use Bluecol 2year antifreeze with IAT. ( inorganic additive technology) it is EG based(ethylene glycol)  and has a bittering  agent added to deter animals etc drinking it as it is poisonous.
If you look on the www.bluecol.co.uk sight for their distributors.
Also the FBHVC give similar advice.
Hope this helps.
John