Corrosion of aluminum alloys Al 6061 and Al 2024 in ammonium nitrate-urea solution

The corrosion behavior of two aluminum alloys Al 6061 T6 and Al 2024 T3 was investigated in a low carbon fuel consisting of concentrated aqueous solutions of ammonium nitrate and urea (ANU). Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques were applied to study the alloys corrosion behavior. Results obtained showed that a corrosion resistance passive film was formed on the surface of both aluminum alloys in solutions of pure ANU and ANU containing up to 1% NaCl. No flawed regions were found on the surface of either alloy after immersion in both solutions for 1500h. However, immersion of the metals into pure 1% NaCl solution resulted in corroded regions immediately after immersion. The results received from weight loss, polarization, and impedance measurements are in excellent agreement. The high corrosion resistance of both Al alloys in the ANU solution containing up to 1wt% NaCl support a safe usage of these materials for construction of storage containers and piping of these solutions.