World's First Laser Rust Remover

Well that's pretty stunning.

In doing some research about the laser, here's what I've found out...

From MachineDesign.com...

The company explains that the device aims short, 1000-W laser pulses at the rusted piece, producing micro-plasma bursts, along with thermal pressure and shockwaves to sublimate the rust and separate it from the metal without damaging the piece. Material removal is halted when the laser is applied to a clean surface because it only sublimates rust. (Sublimation is the transition from a solid to a gas.)

Costs for low-power units start at $50,000. Power supplies can be worn as a backpack for mobile devices, and roll-out generators are available for stationary models. 

From Hackaday.com

So after a bit of research, we find CleanLaser, the German company whose products feature in the videos. Quoting their website: “Powerful, very short, rapid and moving laser pulses produce micro-plasma bursts, shockwaves and thermal pressure resulting in sublimation and ejection of the target material”. So yes, it seems they’re real.

The website is at pains to stress the environmental benefits of the devices over comparable sandblasting or similar technologies, but has very little information on their safety. They are available in power ratings from 12W to 1KW which is a hell of a lot of laser power to be projecting, yet the operators seem only to be wearing goggles. Perhaps this comes back to the “Powerful, very short, rapid and moving” bit in the quote above, is there no point source to sear your retina? Laser experts please enlighten us in the comments.

From, weirdly reddit...

They work by laser ablation. Basically, the laser is bright enough and focused enough that anything that absorbs the light strongly will get heated to a plasma.

A CO2 laser can put out ~1000 watts of power in the infrared (10 µm) that can be focused to a strip or spot smaller than a millimeter. A material that absorbs at that wavelength will be heated very quickly. At lower powers you can use this for laser engraving. But for rust removal you can dump enough heat into the rust to heat it to a plasma.

Now, why doesn't the laser continue to burn away the iron underneath the rust? Because metals reflect light very well, especially in the infrared. I found this plot showing how at 10 µm even iron makes a very good mirror. So once the rust burns off, the laser reflects off the iron rather than heating it up.

edit I talked about CO₂ lasers as an example, but I think many rust removal systems actually use diode pumped YAG lasers (1.06 µm wavelength). See here for instance. The mechanism is still the same (laser ablation). A YAG laser will be less damaging to skin (since water absorbs less), but I would be more nervous about eye damage (it is harder to filter out 1.06 µm light from visible light compared to 10 µm).

Removing Rust with Laser
Here is a machine that uses laser to remove rust and paint from metals. So COOL!
Posted by Hashem Al-Ghaili on Friday, March 25, 2016