How to remove rust and mill scale from metal using vinegar hack.
Here is how I clean new and rusted metal using 5% cleaning vinegar. I like to soak all material new and used in Vinegar for a minimum of 24hrs to help prep materials. Vinegar can normally be found in 5-6% concentrations at just about any store. 20-30% vinegar is stronger but the price could jump to $30 per gallon versus $1-2 for the lower concentration.
Mill scale and dross can be removed easily using 5% vinegar and that's how I prepare the monograms I cut on my CNC table.
If there is any questions lets me know. I will post link to stronger vinegar that can be found at home depot.

Homedepot and other examples of vinegar I have used.

128 oz. 30% Vinegar All Purpose Cleaner Concentrate
https://www.homedepot.com/p/Harris-12...

Heinz All Natural Original Multi-Purpose Extra Strength Vinegar with 6% Acidity, 1 gal Jug
https://www.walmart.com/ip/Heinz-All-...

Calyptus 45% Pure Super Concentrated Vinegar | Dilutes to 9 Gallons | 9x Power Concentrate Vinegar | 1 Gallon
https://www.amazon.com/Calyptus-Stron...