MSE Seminar: Omar Lopez-Garrity, Corrosion Inhibition of Aluminum Alloy 2024-T3 by Selected Non-Chromate Inhibitors

PhD Candidate advised by Dr. Gerald Frankel, Department of Materials Science and Engineering, The Ohio State University

Abstract

High strength aluminum alloy 2024-T3 is commonly employed in aircraft structure and design.  Its improved mechanical properties are attributed to the addition of Cu and Mg that segregate to form strengthening particles.  However, the resulting heterogeneous microstructure of the alloy increases its susceptibility to localized corrosion in the form of pitting and intergranular corrosion.  Traditionally, chromate has been used to effectively inhibit corrosion of aluminum alloys in aerospace applications, but despite their excellent performance, chromate technologies exhibit high toxicity and carcinogenic effects.  Therefore, there is a considerable effort to find chromate-free alternatives that provide the same level of protection as chromate.

The objective of this study is to fundamentally understand how selected chromate-free inhibitors impart corrosion inhibition on aluminum alloy 2024-T3, with the intent of developing the kind of understanding that was accomplished with chromate and other non-chromate inhibitors.  The inhibitors considered include molybdate, silicate, and praseodymium.  These have been found to be present in recent aerospace primers that provide good protection.  Furthermore, since most inhibiting conversion coatings and pigments act by releasing soluble species into local aqueous environments, it was of interest to perform these studies in aqueous solution.  The results reveal that molybdate and silicate impart strong anodic inhibition, while praseodymium effectively reduces the effect of oxygen reduction on the alloy surface.   In addition, strong synergistic behavior was observed when mixing inhibitors in solution resulting in much lower threshold concentrations for corrosion inhibition.

Bio

Omar joined the Fontana Corrosion Center (FCC) in fall 2008 to solve real world problems.  In 2012 he received his masters in Materials Science and Engineering while pursuing his PhD.  His research interests include corrosion inhibition of aerospace aluminum alloys.  Prior to joining FCC, Omar received his bachelors in Mechanical Engineering from the Ohio State University.  He is looking forward to the opportunity to apply his interdisciplinary background and knowledge in the in the field of consultancy and failure analysis.