Not familiar with the specific product but the process has been around for awhile.
It uses an electrolyte solution (usually an acid) with mechanical brushing and a power supply scrub the surface layer off the weld/adjacent base metal. It's a type of electrochemical cleaning process usually used for stainless steel when corrosion resistance is the main concern as the heat tint left from welding can be susceptible to corrosion in service. The cleaning process removes the very thin oxidized layer that causes the heat tint and restores the normal chromium oxide barrier that gives stainless it's corrosion resistance.
The main advantage of that style of removing heat tint is the portability, I believe the best corrosion resistance is still by passivating the entire weldment in a bath. Obviously if you have a gigantic part that may not be possible so they use machines like that instead.
Based on the back of the electrolyte solution on Stahlwerk's page, that's one of the toxic types of cleaning solutions. Some manufacturers make "non-dangerous" electrolyte fluid.
https://www.stahlwerk-schweissgeraete.de/Electrolytecleaner-for-weldingseams
The label shows UN1805 which is a Phosphoric Acid solution and hazard class 8 which is pretty nasty stuff.
