Method and compositions for cleaning aluminum cans

A multi-stage washing method for cleaning an aluminum or aluminum alloy container, the method comprising:

• adding to an acidic wash stage solution having no fluoride ions and having a pH≤2.5 a neutralized fluoride-containing accelerator solution in an amount sufficient to supply the resulting fluoride ion-containing wash stage solution with between 3 to 15 ppm fluoride ion without altering the pH and without exposing humans to increased levels of hydrogen fluoride or ammonium bifluoride toxic to humans;
• wherein the accelerator solution is a stable, neutralized, aqueous ammonium bifluoride solution stable at between 0° C. to 50° C. and having a pH of between about 6 to about 7, and the accelerator solution is stabilized and neutralized with potassium hydroxide;
• and
• contacting the aluminum or aluminum alloy container with the resulting fluoride ion-containing wash stage solution to clean the aluminum or aluminum alloy container.