how do lasers remove rust from rust without burning through the whole thing?


Can anybody explain the types of lasers and how it works?

In: 1

Rust is dark and the underlying metal is light. The laser light quickly heats up the surface and the difference in temperatures causes the rust and contaminants to change size at a different rate than the substrate and thus leave the surface. It kind of blasts the rust with energy causing it to pop and blow off.

1. The temperature at which the rust literally evaporates, is lower than the temperature at which the underlying material evaporates. It’s easier to heat and vaporize the rust.

2. More importantly the lasers are pulsed over a very very short duration (a few femtosecond, that’s a millionth of a nanosecond) and kept moving so that it does not cause a significant thickness of the underlying material to evaporate. The short duration of the laser ensures that the heating of the rust or the top layer is not transferred to the lower layers.

So, to really ELI5 this, the laser vaporizes the rust at a specific location very very quickly, and then stops or moves on before it can cause significant damage to the underlying material.

The process is called laser ablation, and you can find more details here: