Vinegar
Vinegar (acetic acid) is something often used to remove rust on cast iron cookware (and other things).
Also for food! Apple cider vinegar, rice wine vinegar, balsamic vinegar, malt vinegar, etc.
Back to rust, there are a few other types of vinegar to be aware of.
Distilled, White Vinegar (also for food) is a common household item, mixed with water to around 5% acidity.
Cleaning Vinegar has a higher acidity, and may be mixed with other chemicals and fragrances.
Industrial Vinegar can have very high acidity levels (30% to 75% !) and needs to be treated as an industrial chemical.
Pay attention when you shop!
Most of the posts I see say to use distilled, white vinegar dilluted 50/50 with water, for no longer than 30 minute intervals, followed by rinsing and scrubbing to remove rust from cast iron pans.
Repeat as needed.
Could not find a great link to share, but this one is OK:
Learn more about which types of vinegar are best for cleaning nearly everything from the kitchen sink to the bathroom floors.
www.bobvila.com
Philbert