Well every day is a school day - went down the rabbit hole trying to understand why this is such a difficult one and found out things I didn’t learn in a Chemistry class! Found some handy charts! Turns out Titanium and Magnesium are pretty as dissimilar as it’s possible to get! Although based on the info below - pretty much any other metal will corrode Magnesium. The aim of an anti seize compound is to create a barrier between the 2 metals - often by using another metal that sits between the 2 dissimilar metals on the chart. But as you can see - Mag is so different in voltage to all of the other metals this is difficult. So if you are going to do it - then ideally you need a none metallic anti seize and never get the bike wet - in fact according to the info below it’s kind of a miracle that Magnesium doesn’t just turn to dust on contact with air...... “Whenever different metals are positioned in an electrolyte within close proximity to one another preferential corrosion becomes an important factor to be aware of. Galvanic corrosion typically attacks junction areas of dissimilar metals and occurs when the following three conditions are met. Condition 1: Metals must have a galvanic incompatibility (voltage difference - see below table). Condition 2: An electrolyte must be present (water is a good example). Condition 3: There must be an electrical conducting path between the metals. The galvanic series chart below shows metals and their electrochemical voltage range (relative activity in flowing sea water). A typical rule of thumb is that voltage differences of 0.2 Volts or more suggest a galvanic corrosion risk. Generally speaking the further apart the metals in the galvanic series the greater the risk of corrosion, with the metal being of least noble (Anodic) class typically corroding.”
Good man - you found the galvanic series/dissimilar metals charts! This is why magnesium alloys are never used in commercial aircraft - they corrode to buggery on contact with anything +electrolyte!
Have to disagree about lubrication - all nominal torque values are for parts with "light oil" applied. You'll see from your Ducati manual that there is lubricant (oil or grease) or thread lock (which also acts as a lubricant during assembly) applied to every bolt/nut for their given torque figures.
Out of interest, are the brake disc threads on your mag wheels straight into the magnesium or do they have some kind of insert like a helicoil? The limiting factor for a torque setting straight into mag would be the magnesium female thread and not the strength of the bolt. Obviously whatever is there works but maximum torque setting for a M8 bolt into steel is higher than the same into Aluminium which in turn is higher than into Magnesium.
Agree. All to do with the length of thread engagement. To apply the same bolt tension (or tightening torque) in different materials, the thread length is increased/decreased so as to control stress in the threaded material (assuming the same bolt material is used for all). This is why a steel nut is about the same thickness (thread length) as its bolt, and the threads in your Aluminium cases are about three times as long...
im unsure mate. im to pic em up tomorrow from the powdercaoters. the only thing i no is the powdercoater has crac tested em and applied some sort of coating pre powdercoating. dont no if the inserts (if the wheel has em)would be visible after the coating? sorry, my laptop has a button missing.. any guesses as to which one?
It will be a primer as the powder doesn't like to stick to mag without it. You should still see if they have a insert. I would be surprised if they don't but who knows.
yes a primer but specific to mag, cant remember the name. the man nos his stuff and has the ability/certified? to crac test mag. i would imagine the wheel has inserts given what yoal have said about the properties of mag. im sure marchesini dont turn out crap...or do they?!
Seeing as we're already here... Every day's a school day: Carbon Fibre material's galvanic-corrosion potential.
I think they are probably as good as they come but longevity is a issue. OZ guarantee their mag F1 rims for 1000 km . That's the forged ones. The cast ones are 300 km. You had them checked so they are good now. I wouldn't have them powder coated personally but chromated instead. Can't crack check through the powder coat in years to come.
see! you are here to help!!! ive no idea what you just said but it sounded helpful. love you ric.y x....
unless i have an incident where i thin. the wheels may have been damaged, is there any need to chec. em on a regular basis? it cost me 320 to have em stripped, tested, primed and finished so if i had to do that every 5 years or so it wouldnt be the end of the world... or is it not that simple? i really dont no!
