Laser Surface Processing on 7xxx Al Alloys to Improve Corrosion Resistance

7xxx aluminum (Al) alloys are being considered as a higher specific strength material for lightweight automotive structural applications. Such high strength Al alloys have general and galvanic corrosion concerns for multi-material joints that must be overcome for transportation applications. In this present work, a laser surface processing technique was applied to 7xxx Al alloy samples to locally modify surface morphology and chemistry to improve corrosion resistance. First, various laser processing parameters such as laser power, pulse duration, beam size, and scan speed were applied to minimize cracking of 7xxx Al alloys. Then, optical, and advanced electron microscopy techniques were used to characterize changes of surface profile and elemental composition before and after laser surface processing. Electrochemical impedance spectroscopy (EIS) technique was employed to study corrosion resistance for laser surface modified and 600 grit (control) surface finished samples under 0.1% NaCl solution. From EIS measurement, laser surface processed sample improved surface corrosion resistance by at least a factor of 3 compared to the control case.