Al, Phosphoric acid also is the main ingredient in Kano Laboratories® and other De-Rusting chemicals. It will also remove oxide scale from gun parts that have gone through a fire or from hot rolled steel. Jesse the Tennessee Redneck. Ah, so! I was unaware of that. Only use I had seen for Phosphoric Acid was in etching Steel as in Art Class. Al MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.