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Old 01-19-2012, 07:28 AM
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Default ti bolts, graphite and loctite?

I was thinking of replacing the three bolts that hold the alternator in the left side cover with titanium items. Now you have to grease them with some sort of graphite grease (molykote?) which I got from the seller of the bolts, but you´d also have to loctite them in there.

Does the grease interfere with the loctite?
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Old 01-19-2012, 04:57 PM
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If the spec requires Loctite then you can't use anti-sieze grease needed for use with any titanium fastener. So this connection may not be suitable for a titanium replacement.


Titanium and Stainless Steel Fasteners

One of the design considerations for a motorcycle is corrosion resistance. So when you disassemble it, make changes or replace components, and reassemble it, you need to be aware of a few things.

Galvanic Corrosion

The manufacturer uses a number of different metal alloys, plastics, and coatings - each selected for its cost, weight, strength, appearance, and corrosion resistance among other things. What also needed to be considered, is that when any two different metals touch each other, electricity flows between them (which is how a battery works), and the surface of the metal lower on the list (below) corrodes.

For example, when aluminum or magnesium are in contact with carbon or stainless steel, this galvanic action will corrode the aluminum or magnesium. So the approach is to use steel fasteners to fasten steel parts together, whenever possible.
One problem is that aluminum fasteners aren’t very strong, so aluminum parts are held with steel fasteners, but in special ways to reduce corrosion. Carbon steel bolts threaded directly into aluminum is generally avoided, for example.

Here’s a list of some commonly used metals. The farther apart (top to bottom) on the list the two materials are, the more corrosion that will occur to the material lower on the list when they are held in contact.

Gold
Graphite
Silver
Stainless steel, type 316
Titanium
Nickel (passive)
Silver solder
Bronze
Copper
Brass
Tin
Lead
Cast iron
Mild steel
Aluminum
Cadmium
Galvanized steel
Zinc (commonly used as a sacrificial anode in marine environments)
Magnesium

One way to control this galvanic corrosion is to use metals closer to each other in the above list, or by electrically-isolating metals from each other. Cadmium plating of steel fasteners for example, is used to reduce the metal dissimilarities with aluminum and magnesium. Paint and coatings are used to prevent metals from touching.

Keeping the two dissimilar metals dry will also slow the corrosion process but just the moisture in the air on a humid day is enough to cause a problem.

Anti-Seize Products

If a fastener won’t get disassembled for long periods of time, it’s a candidate for using an anti-seize compound during assembly. There are three formulations widely available based on copper, aluminum or nickel.

The way anti-seize compounds work is by placing a third dissimilar metal between the two base metals. So the corrosion of a thread in a magnesium part caused by a titanium bolt is reduced by an intermediate copper-rich or nickel-rich thread coating grease. The aluminum anti-sieze compound is for use between (say) stainless steel and magnesium.

Torque Values

If the same materials are being fastened together, then they are assembled dry to the manufacturer’s torque values - unless otherwise specified. In critical fasteners such as the axle nut that holds the rear wheel on superbikes, the spec calls for lubricating the threads prior to assembly. The torque spec assumes a lubricated thread. Read your manual.

In general, a thread treated with either an anti-seize or regular grease requires a lower torque value (than a higher-friction dry thread) to create the same tension in the fastener. So, if you make a modification that changes a component material, such that anti-seize is now needed, you’ll need to torque the fastener to an approximately 10% lower value to avoid over-tensioning the fastener (according to Machinery's Handbook, 25th ed.). A new torque wrench is usually accurate to ± 3%.

Vibration

If a bolt is torqued to the specified value there’s no need for thread locking adhesives. When the manufacturer is designing a critical connection that will be subjected to vibration, a lock washer is incorporated to prevent loosening.

So to sum-up, if you use titanium hardware to replace the cadmium-plated steel hardware, you can develop worse corrosion problems. The cadmium is sacrificial in the sense that it corrodes preferentially, thereby protecting aluminum and magnesium components assembled by/to it.





It depends on how the titanium (in fact, any material) fastener is used. The above picture shows the galvanic corrosion of an aluminum plate (after just six months) caused by using a stainless steel screw. The stainless itself doesn’t corrode, it causes the aluminum to corrode. The corrosion using a titanium fastener will be worse than for stainless.

In the above situation if you used a cadmium-plated steel screw (like Ducati stock hardware) the cadmium plating would corrode first, and in doing so, protect the aluminum part instead of the other way around.

In fact, that’s what you’re seeing when you’re looking to replace that scruffy-looking hardware ... the inexpensive fastener’s plating protecting the expensive aluminum and magnesium parts.

So, what I’m warning here is that if you replace your corroded fasteners with a corrosion-resistant (but more-dissimilar) material such as titanium or stainless steel, you can shift the corrosion to the aluminum or magnesium if the two dissimilar metals are touching. Anti-sieze materials will help by inserting a third material that itself will corrode but slow down the galvanic action.
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Old 01-19-2012, 08:55 PM
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When switching to Ti fasteners, I was told you could use either loctite (blue) or anti-sieze to prevent galling. Apparently the loctite forms a film that keeps the two metals away from each other. I've always just used a good anti-sieze, so I don't know for a fact if the loctite thing is true.(It was what I was told). Drop Fred at Yoyodyne an email...He'll give you the skinny.
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Old 01-19-2012, 09:55 PM
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Shazaam and Tornado, thanks a lot. The bolts I was referring to might not be suitable for exchange to ti-bolts then as it seems. I will put the stainless screws back in. Thank you!
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Old 01-21-2012, 11:47 AM
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Mate, if you use stainless bolts that may actually aggravate the corrosion even more.

Take a look at Shazaam's table of standard electrode potential and you'll find stainless steel to be even further away from e.g. aluminium than titanium is.

If it's weight reduction you're after titanium bolts can certainly make a contribution in the right direction (lighter bike) provided you've exhausted most other options first. The reason I'm mentioning this is titanium bolts are very expensive and offer a modest contribution compared to, say, swapping to a lighter battery.

As for the galling/galvanic corrosion it certainly is a factor to consider but if you keep your bike clean and out of rain even ordinary grease is going to retard and perhaps even prevent damage caused by galvanic corrosion altogether.

The worst case scenario (in my eyes) is to screw titanium screws into magnesium parts, leave it dry (as in using no grease, anti-seize agent or Loctite), expose everything to rain, and leave it to corrode for years.

Knowing you, you'll be swapping parts and wrenching that bike of yours so often you'll soon discover if something bad is about to happen.

Myself, I only use plenty of high quality grease because I regularly disassemble/assemble my bike.
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Shazaam and Tornado, thanks a lot. The bolts I was referring to might not be suitable for exchange to ti-bolts then as it seems. I will put the stainless screws back in. Thank you!
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Old 01-22-2012, 09:34 AM
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Sten, I am not sure what kind of alloy the side covers of a 2v engine (and probably 4v engine) is made of. The factory used stainless bolts with thread locker in there so I´ll just stick with them.

Regarding weight reduction, it´s just one minor thing that made me want to do it. I started removing some bolts and most of them were corroded. My bike is from England and the PO didn´t care too much for it as it seems. Titanium bolts have the advantage of not corroding, I also like conical heads and the silverish finish of titanium. It just looks fabulous. Moneywise I should have invested in a LiFePo battery, true. Maybe next winter. I also have a super heavy steel subframe on my bike, which is some 2 kilos heavier than the alloy pendant. I wanted to start somewhere and now that I opened the pandora can of titanium bolts, it´s hard not to freak out. I´m sure you know what I mean. Maybe I can keep this bike longer than the other ones, so it will have the time to develop. Chances are good that it will stay at the moment!
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Old 01-22-2012, 08:25 PM
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I see what you mean, Ben. Wanting to upgrade ones Ducati is an addictive desease

I was a bit surprised to hear about the stainless steel screws being OEM/stock on your Hyper, though.

Are you sure about that?

Normally, Ducati uses steel screws (not stainless, mind you) that are cadmium coated. The coating gives these screws a yellowish colour so they're fairly easy to spot...

If the screws you are referring to are silver coloured with no yellowish tint then you may very well be right as to your assumtion regarding stainless steel vs. "ordinary" steel.

If they are indeed stainless you'll sometimes find an A2 or A4 marking on them.
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Old 01-22-2012, 08:52 PM
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You got me there, they´re steel. Not stainless steel. Sorry for the misinformation. I was referring to the stock bolts.

Have you ever tried to replate them? They are in fairly good condition but simply look horrible.
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Old 01-23-2012, 09:39 PM
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Sorry, Ben. I've never tried to re-plate bolts but I have heard of people doing it.

Supposedly, you're not allowed to use cadmium for plating anymore due to environmental law restricting such treatment but I know it's done from time to time anyway.

Then again I don't think stock Ducati bolts are very expensive. Instead of having your screws re-plated you could perhaps buy new ones...
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Old 01-23-2012, 09:46 PM
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Hm, nah, I´d rather replace them with titanium bolts. But thanks for the heads up!

When are we going to see a 998R hotness build thread?
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Old 01-24-2012, 01:08 PM
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Default Ti Bolts

Anti Seize and Safety Wire.
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Old 01-26-2012, 09:11 PM
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Now this is info I needed; thx!
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Old 01-27-2012, 10:02 PM
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Soon, Ben. I hope

As usual, I'm behind schedule but I'll try to post a few pictures over the next few weeks.
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When are we going to see a 998R hotness build thread?
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