Here is a way that you can quickly rust cast iron and steel. First,
please be sure to do this in a well ventilated area and protect your
lungs, eyes and skin from overspray and fumes.
First spray the steel object with Muriatic Acid from the hardware
store. Let this dry overnight. The next day spray the steel object
with hydrogen peroxide, the weak kind from the drug store. Let this
dry overnight. Finally, rinse the steel object with large amounts of
clear water and let dry. Some of the superficial rust will brush off,
but underneath will be dark mature rust that sticks to the steel
object very well. I would practice on a scrap piece before I tried it
on the final object.
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