Which method is used to remove rust and mill scale from steel?

The method used to effectively remove rust and mill scale from steel is acid cleaning. This approach typically involves the use of acidic solutions that react with iron oxides (rust) and other contaminants on the metal surface. The reaction of the acid with rust or mill scale helps to dissolve these unwanted materials, allowing them to be rinsed away, leaving the underlying steel clean and adequately prepared for further treatment, such as painting or coating.

Acid cleaning is often utilized in industrial settings where heavy corrosion is present, as it can achieve a high level of cleanliness that is critical for ensuring proper adhesion of protective coatings. It's important to note that while this method is effective, it must be carried out with caution, utilizing appropriate safety measures and neutralization procedures to handle the acidic waste created during the cleaning process.