Yes as the name implies, this is a
rust eraser. This simple device is designed to erase rust off metal. It is simple and easy to use.
It can work wet or dry, with experimenting you will quickly work out which works better for your situation.
You can also remove some of the plastic casing and create a brush for lighter effect. See picture 2.
This image shows what just a few seconds work can achieve. See video below for more detail
Works considerably better than steel wool and won't scratch the metal surface like sand paper. In fact if applied carefully and water lubricant used where required it wont leave marks. Please remember to dry off any water and to wax polish the metal after cleaning.
Also perfect for removing black pitting on an otherwise polished surface. With a bit of effort any rust or corrosion can be erased from any type of metal.