An exhaust tip is the last thing the gas touches and the first thing an owner sees. It has to survive the same heat as the rest of the run, stay aligned with the bumper, and still clean up after months of road grime. A tip that only looks good on the bench is a short-lived part.
It also has a structural role at the outlet. A titanium exhaust tip carries the exit tube past the bodywork, so it needs enough wall to hold its shape and enough length to clear the bumper without drumming against it.
Stainless steel forms an oxide layer too, but it stays essentially colourless in service. The oxide on titanium grows in a controlled way with heat, and because that film interferes with light at the surface, it shows as colour. The film is only a few wavelengths thick, which is why the shade shifts as it thickens.
That means the tint is not decoration applied afterwards. It is a record of the temperature the metal reached, produced at the surface itself. Two tips from the same batch can therefore differ slightly if one sat in the fixture a little longer than the other.
The colour comes from heat. As titanium is warmed in air, or in a controlled atmosphere, the oxide film thickens and the reflected colour moves through straw, gold, purple and blue. The fabricator stops the process at the shade they want and then keeps the part out of further heat cycles that would push it past that point.
Because the effect depends on temperature and time rather than any added material, it is repeatable but sensitive. Producing a matched pair of tips means treating them as a pair through the whole process, not heating them separately and hoping the result lands in the same place.
Nothing is painted or plated, so there is no layer to flake, chip or peel. The oxide is part of the metal surface. That is the practical advantage of the finish, and it is also why it cannot be polished back on once it has been removed.
The flip side is that heat keeps acting on the surface in use. A tip that is already at its final colour will drift further if the exhaust runs hotter than before, so the shade can shift over the life of the car rather than staying frozen at the day it was made.
Fit is decided by the outlet diameter, the angle of the exit and the amount of clearance to the bumper. A clamped or slip fit is simplest when the tip may be removed later. A welded tip is more secure and gives a cleaner joint, but it commits the outlet to that shape.
Alignment matters more than most owners expect. A tip that is slightly rotated or too short will look wrong from behind, and a tip that touches the bumper will transfer vibration into the bodywork. Where a tip is trimmed for length, the same care used across other titanium fab components applies.
Road film, soot and brake dust do not damage the oxide, but they hide it. A soft cloth and mild soap restore the surface without removing the colour. Abrasive polishes are the one thing to avoid, because they cut through the thin film and leave bare metal that will not match its neighbour.
If the finish does need redoing, it has to be brought back with heat by someone equipped for titanium work. Attempting to touch it up cold will only leave an uneven patch, and that patch will be obvious next to the original surface.
