Ducati Sporting Club UK
Shazaams! Posts
Collected copies of Shazaams! Posts A variety of Technical issues are discussed in this forum. However, the Ducati Sporting Club or any authors cannot accept any liability for the accuracy or content of this section. Anyone attempting modifications on the basis of any information presented does so entirely at their own risk !
Thread Tools Search this Thread Display Modes
Old 20-Mar-2004, 16:36
Shazaam!'s Avatar
DSC Member Shazaam! Shazaam! is offline
DSC Club Member
Big Twin
Posts: 1,167
Join Date: Nov 2001

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 one of the metals 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 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.

18-8-3 Stainless steel, type 316 (passive)
18-8 Stainless steel, type 304 (passive)
Nickel (passive)
Silver solder
Nickel (active)
Stainless steel, type 316 (active)
Stainless steel, type 304 (active)
Cast iron
Mild steel
Galvanized steel

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. Stainless steel and cadmium plating are used to reduce the metal dissimilarities with aluminum and magnesium. Paint and coatings are used to prevent metals from touching.

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. A new torque wrench is probably accurate to ± 3%.
Old 20-Mar-2004, 23:25
Iconic944ss's Avatar
Iconic944ss Iconic944ss is offline
Registered Forum User
WSB Hero
Bikes: 1993 - 944SS & Aprilia Falco
Posts: 7,794
Join Date: Oct 2002
As always Sire an excellent and timely post.

We use products called Copper-slip and Nickel-ease in the chemical plant I now work at. Nickel-ease especially in petrochemical applications.

Copperslip works well for automotive use the only draw back being if it gets on clothing its very, very difficult to get the stain out - but worth the effort.

I'll show the article to my wife as proof that I need to continue buying all the stainless fasteners going for my Duke

Cheers - Frank

[Edited on 20-3-2004 by Iconic944ss]
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes
Postbit Selector
Switch to Vertical postbit Use Vertical Postbit

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Recent Posts - Contact Us - DSC Home - Archive - Top
Powered by vBulletin 3.5.4 - Copyright © 2000 - 2023, Jelsoft Enterprises Ltd. - © Ducati Sporting Club UK - All times are GMT +1. The time now is 08:18.