When trying to strengthen a rusty sword, the process typically involves carefully removing the rust using a series of progressively finer sandpapers (e.g., 220, 600, then 1500 grit), smoothing out the scratches, and polishing the blade. This may be followed by buffing with a compound and using power tools cautiously to avoid overheating and damaging the blade's temper. If the sword is heavily pitted or structurally weakened by rust, it may not fully restore its strength and could be unsafe for use. Additionally, there is a fictional context in manga where strengthening a rusty sword turns it into an overpowered magic sword, but in practical terms, restoration focuses on cleaning, polishing, and inspecting for safety.

If interested in detailed restoration methods, the process includes:

• Removing rust with coarse sandpaper.
• Refining the surface with finer sandpaper.
• Polishing and buffing for shine.
• Avoiding overheating during power tool use.
• Inspecting for severe pitting that compromises blade strength.

This is the common practical approach to "strengthening" or restoring a rusty sword's usability.