What you are trying to do is called "Pickling", chemically removing mill scale. The most popular chemistries to do this are hydrochloric or sulfuric acid. Prepare a bath with 8-10% HCl and water and place your parts into it. At room temperature to remove all the scale will take about 5-10min. If you heat the bath the pickling speed increases. Industry runs in baths at 60-70C just to give you an idea.
After pickling you must rinse the parts throughly, otherwise the acid will continue to etch away. Following the rinse, coat the parts with a light oil as they will start to rust very quickly.
Be very careful around HCl it is quite corrosive. I suggest that you not do this indoors. The hydrogen chloride effluent will cause metals to corrode, and the by product of etching Fe is H2. Wear chemical gloves and an acid apron as well as a face shield and remember "AAA". Always Add Acid to water not the other way around!!! |