I am fairly sure this has been on here before but in case I am going mad.
Rust has 6 water associated with the molecule Fe203.6 (H20).
The laser boils the water and turns it into super heated dry dissasociated steam and in doing so it blasts the rust from the surface.
It was tried 30 years ago for use on rolling & extrusion billets with limited success.
It worked but was not economical when compared to a man with an angle grinder or scabble gun.
The Aluminium industry then ran with it as oxide on the surface of aluminium billets rips up the roll face.
They also trialed plasma guns again with limited success.
Looks like the control units have gotten better & lasers have gotten cheap enough to make it viable.