Conversion Coatings Formation on 2024 Aluminium Alloy: The Effect ofCleaning Pre-treatments

摘要

The effect of cleaning pre-treatments on Al alloy 2024-T3 before conversion coating wasrnfollowed using electrochemical techniques, while the operations of alkaline etching, waterrnrinsing and desmutting were undertaken. When performing the pre-treatments, the variation inrnthe open circuit potential spans from –1.6 to ～ -0.1 V(SCE) suggesting not only that aluminarndissolution and the corrosion of copper rich intermetallics occurred, but furthermore, thatrncopper oxidation/ reduction might take place. SEM and EDAX of the resulting surfaces agreernwell with electrochemical data.rnVoltammograms were conducted Al alloy 2024-T3, on pure copper and on Al, in order tornidentify critical potentials when in contact with alkaline and acid solutions and its relation tornthe open circuit potential registered during the pre-treatments. Results suggested thisrnprocedure as a fast method to investigate the conditions for optimal pre-treatment, with thernuse of more sophisticated techniques, such as RBS and TEM, reserved for conditions closer tornthe final selection of pre-treatments.rnThe effect of pre-treatments on the efficiency of Ce based conversion coatings growth isrndiscussed.