My theory is they have thousands of gallons of the stuff the Russians sold/gave them?? (nothing the Russians give you is free)?? I would suppose it is some industrial coating to prevent corrosion??
Most of the time aviation wheels are aluminum, and have a light coating of zinc-chromate, for corrosion resistance, and then a light white or silver, so that brake fluid or a leaking wheel bearing grease will leave a visible "streaking" on that light colored surface.
I recently serviced the wheel bearings on our airplane, and spent a good deal of time at the parts washer, cleaning the grease, dirt, grass stains off of the exterior of the wheels.. the Cessna we fly has a wheel bearing race, a tapered roller bearing which is greased after cleaning, a metal washer, a felt washer, and another metal washer retaining/protecting the felt washer, and is retained on each side by a snap ring, whose purpose is to keep dust out, and grease in!
Actually Kwai, that is NOT John Deere Green, which is a much lighter brighter color,,,, (yes it is proprietary) and goes well with John Deere Yellow,,, ( which is also proprietary),,, that color is actually the color of a tractor from a former soviet block country, (East Germany), the Deutz, which were imported in vast numbers after the "Iron Curtain" fell.
They were decent, simple, and cheap,, rather crude compared to domestic tractors? kind of like the current Kubota's and Mahindra's....
the Russians must have also given Webby a bunch of the stuff for the SDF, as he has that splashed all over our current header! eh Webby??? actually Webby's header is closer to John Deere Green, and we know Webby is a "Southern Boy"!
any way, its just an odd color, and I'm surprised the Chinese have copied the Russian practice of putting this ugly stuff on airplanes,,, it does detract from the overall appearance of an otherwise extremely beautiful airplane!
so its just kinda "quirky" in my opinion, and I love flankers, particularly in primer,,,, I just love Zinc Chromate, and I love seeing the different coatings applied on the many and varied materials about the airframe... (it also adds fuel to the discussions of "whats it made of"), LOL
