Hi Guys,

Isn't corrosion weird? Check out the underneath of my rear brake pedal; it's quite far gone. I think others have had this problem - was it Sidecar Paul mentioned he's changed one or two? Is it a problem only for us western Europeans or does it also go bad in hot climates like Aus?

Anyway, changed it out for a good one.

Cheers
Dave

I had the same thing happen to the rear brake arm (drum brake) on my R80. The aluminium seemed to de - laminate. I'm not sure whether they are sand cast or die cast but a very odd form of failure. John

k100virgin wrote:I had the same thing happen to the rear brake arm (drum brake) on my R80. The aluminium seemed to de - laminate. I'm not sure whether they are sand cast or die cast but a very odd form of failure. John

Yeah odd isn't it John? I didn't think of aluminium being a laminated kinda structure- if you know what I mean!

Cheers
Dave

wow dave that is weird ....todate havent seen the same

could it be because of road salts ? \

something i dont think we experience at all out here .

I've never seen anything like it Dave, I wonder if we have any metallurgists on the forum? Did it fall out in one lump or flake away?
88

Mine is the same, but not as quite as bad. I suspect it is from salt.

Mine is spotless, even has logo and part number.
Guess you are right with the salt.
Best regards
JAP

Hey Guys, yeah I reckon it must be the salt and the wet. My bike spent much of its life as far south in Engalnd as you can get and I assumed did not get a lot of road salt on it as it is relatively mild there (by UK standards). Maybe it was being in a coastal location - sea salt.

Do they use road salt in Ireland 88? EDIT - ah yes I see you do!

It seems it has flaked away gradually and of course looking at it you'd think it was perect until you looked underneath. Usually a healthy supply of these pedals on Ebay so probably common.

Cheers
Dave

It is called exfoliation corrosion and is known in the aircraft industry.

Mine is a UK bike originally, spent the first half of its life there. Our winters here towards the western part of Ireland are usually milder, but in the last few years the county councils have tended to spread salt on main roads at the merest hint of frost. I usually try to avoid using the bike when the roads are salted, but this winter I have had no choice due to being "between cars" for a while.

Exfoliation corrosion - well you live and learn, thanks. Well I reckon I will put a couple of coats of paint underneath the pedal on the 'replacement'.
Cheers
Dave

Yes, Dave, I have had that on my rear brake levers and if it doesn't occur in Australia, then it probably is caused by our salted roads. On one early lever I kept slimming down the foot piece to tidy up the corrosion, until it was only about 1/2" wide........looked quite racy!

One strange thing, though, is that other alloy parts don't suffer like the brake lever; for instance, I've never replaced a gear lever.

Paul.

Gee guys, I'm starting to think that Japuente has it made . We all should move to Venezuela.
RT

Exfoliation corrosion will not affect all alloy parts at the same speed, as there are many types of alloy. It will have the most effect on alloys with more grain. These parts would normally have some sort of varnish or paint to protect them, but if that protective surface is punctured in any way then that is how it will start. Salted wet roads will make it worse.

It's not quite the same but reminds me of crevice corrosion you get in high grade stainless in a marine enviroment. Rudder shafts are very susceptible to it because of welding. The crevice corrosion comes from the metals not alloying properly at manfacture of the shaft or welding and as a result you get dissimilar metals within the one piece of metal and the salt is an electrolite.
Big difference is that a microscope is usually needed to get that lamination look. Painting may not solve the problem if it is the same as crevice corrosion then a protective coating makes it happen quicker because it holds the electrolite in there in a closed enviroment. I have never seen that in aluminium and I wont go so far as to say it is the same but it does bear remarkably similar characteristics.

exfoliation does occur in aviation a lot and mostly in alloys that are down the galvanic series list approaching those considered
"sacrificial anodes " such as zinc....so things like magnesium exfoliate real quick especially if attached to another alloy such as steel...without a substance ion between to break the flow of electrons....and subsequent removal of material from one to another

The strange thing is that there is no other metal anywhere near it.

perhaps its like a layer cake of dissimiilar metals....like pages of a book.....mine is fine...no electrolytes there...

Rick G wrote:The strange thing is that there is no other metal anywhere near it.

Nor would there need to be. Dissimilar metal corrosion is caused by electrolytic action on the surfaces of two metals, but if you think about it, alloy is a fusion of different metals and if it has a large grain as in a casting, then there is the potential of exfoliation caused by electrolysis.

A great preventative is WD40, we used this in the RAF to protect the undercarriage bays on some aircraft, but it is short term 6 to 12 months.

As we did on various aircraft...3 types of water displacement corrossion preventative WDCP from light WD like rp7 wd40 boeshield etc through to a thick coating used to prevent further degradation particularly for long term preservation.

Found that for example B707 undercarriage doors made of magnesium (light and strong and magically flammable) was bolted to an alloyed main undercarriage with mild steel bolts....and you could almost see and hear it corrode....and don't even start me on Canberra's and vampires and other brit aircraft who wanted badly return to the raw materials they were made from....in OZ the BMW is very resilient but we do not salt...

Vampires! I saw a picture of one of those :-) . I was more involved with Harriers, Jaguars, Tornados and VC10s.

I worked ADV during the gulf war (Khamis Mushayt)...too new to corrode then......

bikerboy wrote:

Rick G wrote:The strange thing is that there is no other metal anywhere near it.

Nor would there need to be. Dissimilar metal corrosion is caused by electrolytic action on the surfaces of two metals, but if you think about it, alloy is a fusion of different metals and if it has a large grain as in a casting, then there is the potential of exfoliation caused by electrolysis.

A great preventative is WD40, we used this in the RAF to protect the undercarriage bays on some aircraft, but it is short term 6 to 12 months.

Thats what I was getting at with the high grade stainless. The uneven mix of metals in the alloying process effectivly gives dissimilar metals.

Found my old brake levers today, down in the garden shed.





They've just continued to corrode away since I replaced them donkeys' years ago.
Paul.

Wow you should call the British Natural History museum, I think that is the Bog Man's
motorbike controls. What a find.
You don't live on the Moors do You?
RT

No moors, RT, just our winter salted roads.
Paul.

My 1984 K100RT rear brake lever did exactly the same so I bought a good/cheap genuine replacement - that was two years ago and it is still sitting in the spares cupboard - one day I will get around to changing it

Wow Paul I hadn't seen the photos, theya re pretty far gone!
Go for it Krambo! Best tenner I ever spent LOL
Dave