lead weight in the clip-ons

[docc]

I just dissassembled my bar-ends on my 'other' cafe racer and found the clip - ons full of powder looking like the corrosion which forms on the battery terminals. Two years ago I had filled them with some lead shot. There has been much discussion of this to damp vibration and my Guzzi has about an once of shot up inside its clip-ons.

 

I know we have a chemist or two on the forum, so I am wondering if the lead and aluminum are forming some sort of 'battery' and slowly turning my clip-ons to aluminum foil?

[jrt]

zzz, snrk, wha? huh? (waking up from sleep)

Quick electrochemistry tutorial. Thermodynamically, you could set up a Pb/Al battery, but practically not with two elemental metals. To make a battery, you need three things 1) a reducing agent (anode) to give up electrons 2) an oxidizing agent (cathode) to accept the electrons and 3) a salt bridge or conductor of some type for the electrons to move through. The reactions don't add up for two elemental metals:

Al --> Al3+ +3e- (E0=1.66V) (very, very energetically favorable)

Pb --> Pb2+ + 2e- (E0=0.13V) (still favorable, but not as much as the Al)

The problem with these two reactions, as written, is that there's no place for the electrons to go, no cathode...(do the bars feel tingly? ...just kidding)

Of course, that's in a beaker. In real life I could imagine that the lead would abrade the aluminum oxide (Al2O3) layer from the inside of the handlebars. You might just be seeing the aluminum oxide dust (and lead dust) from continuous abrasion and reformation of the aluminum oxide.

Background info on the aluminum- the aluminum reaction given above does work- very well- when aluminum metal is exposed to air (water/oxygen):

4Al + 3O2 --> 2Al2O3 Ecell ~2.7V

A large positive "E" value is energetically favorable, and the large positive values associated with formation of aluminum oxide, and conversely the large negative values in the direction of making metallic Al, tell us that aluminum should be very easy to rust away, and very difficult to make metallic aluminum. And this is true- it wasn't until the late 1800's that we developed a reasonable method to produce aluminum metal and every piece that's made immediately oxidizes. But the aluminum oxide which forms on the outermost layer is impermeable, so oxygen/water reacts with the first few atoms on this outside layer and the underlying aluminum remains metallic. Contrast this to iron- it also reacts with oxygen to form Fe2O3 xH2O (hydrated iron oxide is rust), but iron rust is very porous, so the entire piece of metal will eventually rust away.

Because aluminum (in air) always has this layer of oxide, that's why I come up with the idea that the lead shot is mechanically wearing away at this oxide, which is continously reforming and being worn away.

Is the lead shot 'loosely' or 'tightly' packed? Limiting movement of the lead would be one way to prevent abrasion. Of course, It could be an electrochem reaction- what do I know? There's lots of stuff in air that could serve as a cathode. You could put the lead shot in a plastic baggie in the bar to isolate the two metals; that would take care of any electrochemistry.

Damn, all that and I could have just written the last paragraph.

Hope this helped,

J

[twhitaker]

But Professor, Gilligan and I just want to get to the rally. Couldn't we mix it with some latex and pour it in?

[docc]

The abraion theory seems pretty plausible what with all the vibration in the clip -ons. Even though I packed the balls in tightly I imagine the vibration could still continually expose fresh aluminum.

 

I guess I'll dig it all out and repack the lead in grease. I realy don't want to use anything that will harden up as I'd like the option to remove the stuff.

 

I've learned a good chemistry lesson though. If my assessment is correct, the LaPhroig would be the anode, water the conducting agent and my brain - the anode. Stop by when in Lower Middle Muletown and we'll get anodized!

[Guest northend]

I know that when doing electrical (household) that any aluminum cable, wire, or connection that goes to a different type of metal (copper, lead, etc) must have a coating of this special grease to keep them from corroding. There is a chemical reaction between the metals. Weather water or oxygen helps it along, i'm not sure

 

I think I gave myself a headache

[al_roethlisberger]

I mixed my lead shot with SiliconeII sealant before packing it in tightly. I haven't had the bar-ends off since to inspect it for the conditions observed above, but that is one potential option to keep the lead still.

 

All I know is that people have been putting lead shot in handlebars for long time now, so I suspect it's an OK practice

 

al

[jrt]

If my assessment is correct, the LaPhroig would be the anode, water the conducting agent and my brain - the anode. Stop by when in Lower Middle Muletown and we'll get anodized!

Docc,

You have an excellent hypothesis-driven proposal, and I look forward to a productive collaboration to test your thesis.

 

Hey, Northend- you're right, the aluminum oxide that forms on the outside of aluminum is an insulator (about like glass really)- but the real problem with aluminum wiring is that aluminum is just a terrible conductor. Don't ever use it in a house you plan to live in.

J

[Guest northend]

The Aluminum also becomes brittle over time, I think they used it in some houses back in the 60's or so.

The only place I use it is the main feed to the breaker box. Copper heavy enough for 200amp service is a real b--tch to work with .

Just curious, Has anybody tried using steel shot???

[docc]

july 9-11 in Athens, TN, we will be testing the hypothesis that Guzzisti can be anodized in brief evenings between excellent rides in the mountains.

 

i can write you a grant, er a note that is, declaring your presence is required to monitor expected outcomes.

[jrt]

I wish I could go, but I have a prior engagement in New Hampshire (or Connecticut...the east coast confuses me ).

I am going to try and make Luap's rally in MO May 7, though.

http://www.wildguzzi.com/

has the info.

Cheers,

jason

[docc]

Well, you'll be missed. I'm hoping it turns out a few of the faithful that we may admire one another's rides and practice a little cerebral anodization as all Brothers in Guzzi should.

 

Oh and this:

[Guest northend]

I believe a meld has already taken place Of course anodization I believe takes a catalist of single malt scotch AFTER the serpentine twists of the dragon have been tamed

Although my tastes lean more towards JD Black

 

Later........But sooner than you think........Jeff H.

 

P.S. Next time I need a day off i'll call you for a fax (note)

[roberto]

Back to sanity briefly

 

The “battery effect” is known as “galvanic corrosion” and will occur whenever two dissimilar metals are in contact. It’s the same reason that engine bolts seize up easily when steel bolts are screwed into aluminium alloy casings (I am currently knocking lumps out of the front engine mounting bolts on the Scura – it won’t be long before the drill is brought out!). Basically the more electrochemically active metal corrodes before the other one and actually protects the less active metal from corrosion. The obvious example of this is galvanizing (of say a water bucket), where steel is coated in zinc, so the zinc corrodes before the steel and thus protects the steel from corrosion. Several car manufactures galvanize the chassis before painting.

 

Incidentally, the subsea industry uses aluminium-zinc alloy as sacrificial material to protect steel structures – it’s the best for protecting steel! This is similar to the alloy used to make carburettors!

 

I would like to point out that the density of solid steel and lead shot are about the same due to the spaces between the “balls” – it’s just that lead shot is a little more convenient to fill things with. Replacing the lead shot with the right diameter steel bar would give the same result. Melting the lead and forming that into a bar would give you the heaviest result – perhaps pour molten lead directly into the bars for the best result. Most fishermen will know you can melt lead in your own kitchen.

[jrt]

Back to sanity briefly

 

The “battery effect” is known as “galvanic corrosion” and will occur whenever two dissimilar metals are in contact. It’s the same reason that engine bolts seize up easily when steel bolts are screwed into aluminium alloy casings (I am currently knocking lumps out of the front engine mounting bolts on the Scura – it won’t be long before the drill is brought out!). Basically the more electrochemically active metal corrodes before the other one and actually protects the less active metal from corrosion. The obvious example of this is galvanizing (of say a water bucket), where steel is coated in zinc, so the zinc corrodes before the steel and thus protects the steel from corrosion. Several car manufactures galvanize the chassis before painting.

 

Incidentally, the subsea industry uses aluminium-zinc alloy as sacrificial material to protect steel structures – it’s the best for protecting steel! This is similar to the alloy used to make carburettors!

 

I would like to point out that the density of solid steel and lead shot are about the same due to the spaces between the “balls” – it’s just that lead shot is a little more convenient to fill things with. Replacing the lead shot with the right diameter steel bar would give the same result. Melting the lead and forming that into a bar would give you the heaviest result – perhaps pour molten lead directly into the bars for the best result. Most fishermen will know you can melt lead in your own kitchen.

All true- you can sometimes see the bars of zinc on the sides of container ships if the ship is empty.

 

But please don't melt lead in your kitchen- not enough ventilation. Do it outside if you have to do it at all.

j

[twhitaker]

You get a much better effect from lead. Steel weight is .283 pounds per cubic inch while lead is close to .400 pounds per cubic inch. We use lead for counterweights in machine tools because it's quite a bit denser.