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Discussion Starter #1
I heard that Titanium reacts poorly to aluminum. I didn't know this before I bought about $300 worth of Ti. Does this mean that I've put my brake calipers and pinch bolts, among others, at risk? Or is the effect one that is unlikely to ever really be an issue? Please advise. T
 

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Also bear in mind that titanium bits really require special spanners and such because the chrome plating interferes with the integrity of the titanium..

or some such thing..
 

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First I've ever heard of this. I did a lot of titanium conversion on my 916 before the prices went through the roof. Fork pinch bolts, swingarm bolts, caliper bolts, rotor bolts you name it. No problems.

On my 999R I just did three 6mm taper heads when I bought a carbon fiber vented timing belt cover. Around $8 each for those, but the swingarm bolts were $32 apiece, but man did they look good!
 

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Also bear in mind that titanium bits really require special spanners and such because the chrome plating interferes with the integrity of the titanium..

or some such thing..
To clarify, this applies to very old cadmium plated tools. The cadmium from the old tools would deposit onto the titanium fasteners or fittings. Titanium is a strong cathode to cadmium causing galvanic corrosion over time. A model case of this was incidents of the wings falling off the F-111 jet fighter where cadmium coated tools were used on their highly stresses titanium wing pivot bolts.

Newer tools (last 20 or so years..guessing) are chrome or chrome-vanadium plated and do not have this problem. If you are not using your grandfather's inherited tools, you should not be concerned.
 

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I heard that Titanium reacts poorly to aluminum. I didn't know this before I bought about $300 worth of Ti. Does this mean that I've put my brake calipers and pinch bolts, among others, at risk? Or is the effect one that is unlikely to ever really be an issue? Please advise. T
Technically you are correct. Titanium is considered a strong or very strong cathode to Aluminum. As such there is an electrical potential at the interface between the bolt and aluminum part. With time, the titanium will start generating small amounts of surface corrosion on the aluminum parts. However, in practice, that's as bad as it gets unless you are in severely wet high temperature situations. The structural margins of safety used in automotive applications are quite high relative to aerospace applications for example. Losing a couple of thousandths of material off the surface will not pose a structural issue on your bike. In contrast, losing a few thousands on a primary structural element on a jet fighter can bring it down.

If you want to keep your bike looking good, keep it dry and inspect your Ti fasteners occasionally. Breaking them loose and cleaning them when doing maintenance would help. My Ducati comes completely apart every 6000 miles when checking valves anyways. Installing them "wet" with antiseize or very small amounts of moly based lubricant will also help with corrosion, galling and wear. Ti threads are brutal against aluminum threads if they are installed and removed frequently.
 

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Discussion Starter #8
Technically you are correct. Titanium is considered a strong or very strong cathode to Aluminum. As such there is an electrical potential at the interface between the bolt and aluminum part. With time, the titanium will start generating small amounts of surface corrosion on the aluminum parts. However, in practice, that's as bad as it gets unless you are in severely wet high temperature situations. The structural margins of safety used in automotive applications are quite high relative to aerospace applications for example. Losing a couple of thousandths of material off the surface will not pose a structural issue on your bike. In contrast, losing a few thousands on a primary structural element on a jet fighter can bring it down.

If you want to keep your bike looking good, keep it dry and inspect your Ti fasteners occasionally. Breaking them loose and cleaning them when doing maintenance would help. My Ducati comes completely apart every 6000 miles when checking valves anyways. Installing them "wet" with antiseize or very small amounts of moly based lubricant will also help with corrosion, galling and wear. Ti threads are brutal against aluminum threads if they are installed and removed frequently.

Wait you are saying its good to dry and inspect Ti when doing routine maintenance and then you said that the Ti threads are brutal against Al threads.... That seems contradictory
 

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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 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. The aluminum anti-seize 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 a lubricant 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 a 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 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 wiil 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-seize materials will help by inserting a third material that itself will corrode but slow down the galvanic action.

Rust never sleeps.
 

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Wait you are saying its good to dry and inspect Ti when doing routine maintenance and then you said that the Ti threads are brutal against Al threads.... That seems contradictory
Hence the recommendation for lubrication to counteract galling and wear. Please read the post in its entirety and context. You don't get anything for free.
 

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Silver, galling and wear are entirely seperate from galvanic corrosion.

Aniti-sieze are typically composed of nickel or copper dust in a grease. Copper and nickel are still high potential toward corrosion of aluminium.
It's best to use fasteners which have a coating which is more anodic than the part it assembles, i.e. cad or zinc plated.

Using ti fasteners as direct replacements for stock is a bad idea because for same size they neither have the same stiffness or strength as the class 8.8 (or 10.9 for caliper bolts) for which you have replaced.

FYI since when was the F-111 a jet fighter? It was a strike recon aircraft! Aus is the only country still flying them and only other country outside US to have purchased them.
 

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Discussion Starter #12
So to summarize: Ti bolts may not be perfectly suited for fitment with Al but the mildly corrosive properties can be contained to a degree by using anti-sieze. For motorcycle applications Ti bolts are not going to cause problems if the bolts are occasionally checked and re-lubed with routine maintainance. Does that about sum it up?
 

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Silver, galling and wear are entirely seperate from galvanic corrosion.

Aniti-sieze are typically composed of nickel or copper dust in a grease. Copper and nickel are still high potential toward corrosion of aluminium.
It's best to use fasteners which have a coating which is more anodic than the part it assembles, i.e. cad or zinc plated.

Using ti fasteners as direct replacements for stock is a bad idea because for same size they neither have the same stiffness or strength as the class 8.8 (or 10.9 for caliper bolts) for which you have replaced.

FYI since when was the F-111 a jet fighter? It was a strike recon aircraft! Aus is the only country still flying them and only other country outside US to have purchased them.
I made no such connection between galling and galvanic corrosion. They are completely separate phenomenon. The use of a grease to address both does not mean they are connected. Please re-read my post.

"jet fighter" was used as a general term for the layman. I very well know what the F-111 is but chose to use a general term. Unfortunately you felt the need to nit-pick it but even your description is incomplete. But correcting you on it does not add value to this thread....;)

I agree with your concern about the bolt class. Most people do not check equivalency.
 

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So to summarize: Ti bolts may not be perfectly suited for fitment with Al but the mildly corrosive properties can be contained to a degree by using anti-sieze. For motorcycle applications Ti bolts are not going to cause problems if the bolts are occasionally checked and re-lubed with routine maintainance. Does that about sum it up?
Trenman,
The best way to determine the risk is to look at the history of Ti bolt use on motorcycles. Many people have used Ti bolts for street use yet the reports of broken parts or death/injury from their use is absent from forums or news.

I don't use Ti bolts because of the issues discussed here but any suggestions that you have completely screwed up and your bike will kill you as a result of Ti-bolt use is unfounded until someone here coughs up some proof. I believe this is the general concern in your OP.

Use good sense, heed torque requirements, inspect aluminum bits for corrosion.
 

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Discussion Starter #16
My ti bolts are anodized. Does this offer any protection vs regular naked ti? I don't know how the process works but I imagine if a layer is added to produce the color, similar to how it is added to ss bolts, then it may help. Excuse me if I'm completely ignorant of the facts, I am just bummed that I assumed that ti would be fine to use, and I spent what I did on ti bolts to date... Ughh
 

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Discussion Starter #17
From Wickipedia

Anodizing, or anodising, is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. Anodizing increases corrosion resistance and wear resistance, and provides better adhesion for paint primers and glues than bare metal. Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light. Anodizing is also used to prevent galling of threaded components and to make dielectric films for electrolytic capacitors.


Guess so?
 

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Ssled

Thank you for clearing that up.. it's something I was amazed about when I heard a couple of years ago. I got the impression it was modern tools etc. Appreciate the clarification.. I'll remember not to use my dads Whitworth spanners then.


Shazzaam.. most informative as always.. Thanks for expressing it so well

Cheers
 

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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. The aluminum anti-seize compound is for use between (say) stainless steel and magnesium.
The grease in anti-seize products prevents water vapor and liquid water from entering the joint as well, thus preventing galvanic corrosion.
 
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