If you're having trouble getting it off, then it's not Titanium Oxide which a very soft material and crumbles at the slightest touch (which is why it's almost always seen as a powder). It's interesting how Titanium can be one of the strongest materials and its oxide can be one of the weakest.
Some metals oxidize very quickly. Aluminum is the fastest. You have probably never seen a piece of Aluminum that wasn't covered with rust. But, Aluminum Oxide, also known as saphire, is very hard and very clear. So, as soon as it hits air, a sheet of Aluminum covers instantly with rust. But, because that rust is clear, you don't see it. And, because it is so hard and has such a tight crystal structure, it seals the Aluminum. As soon as a layer only a few molecules thick forms, the Aluminum is essentially sealed in an airtight saphire case and, since no air can get in, the oxidation stops. So, the rusting of Aluminum is self-limiting. So, it's not true that Aluminum does not rust. But, Aluminum rust happens virtually instantly and is then self-limiting. So, while Iron Oxide, the familiar red rust of steel and iron metals, destroys the metal, Aluminum rust protects and preserves the metal.
Anyway, as much as Aluminum rusts almost instantly when exposed to any oxygen, Titanium rusts, oxidizes, very slowly and only under specific conditions, most notably very high temperatures. So, it's unlikely that what you're seeing is Titanium Oxide. It's probably some residue left from some solvent used to clean the casting. I'd try WD-40.
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Chuck
Balisongs -- because it don't mean a thing if it ain't got that swing!
http://www.balisongcollector.com
