Ok guys, I've just remembered where I heard how little difference anodizing makes and we are on the right thread for it.
Keith (KMB) built the rear hub for the bike and anodizing was talked about, I'll message keith and ask him to look in.
Sammie, you're putting me on the hot seat! I am no anodizing expert but I'll share what I think I know.
There are several types of anodizing processes and they use different parameters depending on the desired results. The hard anodizing that Brent is talking about is commonly referred to in the USA as Type III Hardcoat. As he mentioned, it is really a treatment versus a coating although there is a buildup. Type III Hardcoat anodizing is a process that forms an extremely hard, abrasion resistant, porous oxide layer on aluminum. It is performed in a sulfuric acid bath at a temperature controlled between 28-32º F. The power supply is DC and is applied with a fairly high current density - usually 24-30 amps per square foot of surface area. The aluminum part being anodized is the anode or positive pole in the DC system. Current is applied to the system for a prescribed time, and at the desired current density to achieve the oxide thickness required. The oxide thickness per surface can typically range from .0007-.003", .7-3mils, 18µ-75µ. Higher thicknesses can be achieved depending on the aluminum alloy being treated. The treated layer is 50% infused into the material - so half in and half out.
The tricky part is finding an anodizing company that can control their process very predictably. Especially when final dimensions are in the .001-.002" range. You have to find a coater that is very confident in controlling their layer thickness and machine the parts over or under accordingly. These were the issues I was dealing with in the rear wheel on the Triple. We were trying to hold final dimensions tighter than .001". This is usually not a big deal where pistons are concerned since the cylinders are bored according to piston size.
Cap'm how can the the extra 0.002" be ignored in cylinder clearance?
It cannot. The cylinders have to be bored to desired clearances depending on the final treated piston size. I will not speak for Brent but I read him to say you can run tighter piston to cylinder clearances with hard anodized pistons than you can with untreated pistons.
