So, what is oxidation?
At the most basic level, oxidation is the loss of one or more electrons from one atom to another. When an atom is oxidized it's properties change. So when a material is oxidized, it's properties also change. Think of iron, for example, when it undergoes oxidation (rust) it is transformed because it has lost electrons. Unoxidized iron is a strong, structurally sound metal while oxidized iron is a brittle reddish powder. In the case of titanium, oxygen takes electrons away from the titanium resulting in the oxidation of the titanium. The oxygen gets reduced while the titanium oxidizes forming a protective oxide layer which helps prevent further corrosion and oxidation.
titanium metal and its alloys oxidize immediately upon exposure to air. Titanium readily reacts with oxygen at 1,200 °C (2,190 °F) in air, and at 610 °C (1,130 °F) in pure oxygen, forming titanium dioxide. It is, however, slow to react with water and air at ambient temperatures because it forms a passive oxide coating that protects the bulk metal from further oxidation. When it first forms, this protective layer is only 1–2 nm thick but continues to grow slowly; reaching a thickness of 25 nm in four years.
Titanium has a strong chemical affinity for oxygen, and a stable, tenacious oxide layer forms rapidly on a clean surface, even at room temperature. This behavior leads to a high degree of corrosion resistance. The strong affinity of titanium for oxygen increases in thickness at elevated temperatures. When heated for half an hour in open air at 650°C the oxide thickness is measured a <0.005 mm (<5,000 nm) thick, compare that to the 25 nm the oxide layer grows at room temperature over 4 years and you will understand the role that elevated temperatures can play in the oxidation process.
A small oxide layer, while impossible to avoid, can be a good thing as it serves as a protective barrier from further oxidation and interstitial elements in the atmosphere. But too much oxidation can have a long term effect on your nail as the mechanical properties of the material change and the titanium becomes more brittle.
So how can we limit the amount of oxidation our nail undergoes?
With titanium, temperature exposure is critical to mechanical and thermal property development. It's a good idea to practice to limit the exposure of titanium to high temperatures to prevent the formation of excessive scale and embrittlement. Titanium is chemically active at elevated temperatures and will oxidize in air resulting in the formation of scale. Learning how to heat your nail up without taking it to a glowing red will significantly prolong the life of your nail.
Water, or moisture is rich in oxygen and hydrogen and should be avoided at elevated temperatures. Quenching or "water seasoning" was an old concept in the community that thought a nail needed to be heated and dunked in water before use. This is not true and can lead to excessive oxidation and scaling, and significantly decrease the life of your nail as the ductility is reduced.
Similarly to quartz devitrification, titanium oxidation can be caused by excessive temperatures, atmosphere, and contact with water. Though the reasons the two materials change are completely different, the methods to avoid them are similar. While the atmosphere is impossible to escape, glowing red temperatures and "quenching" are not and should be avoided to prolong the life of your titanium products.
What's the best way to keep the nail clean from carbon build up?
Torching left over oil is less of a cause for concern with titanium, as it will not devitrify like the quartz, but it will result in the development of a carbon build up. The same "q-tip tech" which has been employed and perfected with quartz works well with titanium. Removing all surface contaminants before torching a nail head will significantly reduce the amount of carbon that builds up over time. Carbon layers that develop can be removed mechanically with a flat head dabber tool or pick without much fear of damage being caused to the surface. A clean, relatively low temperature, surface has produced the best user experience and you can use cotton swabs to make sure your surface stays clean between each use.