Evaluation of Susceptibility to Exfoliation Corrosion of Aluminum 2060-T8E30 using Electrochemical Techniques in EXCO and Modified EXCO Solutions.

Deparment of Chemical and Biomolecular Engineering National Center for Education and Research on Corrosion and Materials Performance The University of Akron.AbstractMany Aircraft Applications for High Strength Aluminum Alloys such as 2060 alloy require having an elongated grain structure in the direction of the plate surface; these particular pieces are susceptible to Exfoliation Corrosion (EFC) due to internal stresses caused by voluminous corrosion products. In this study electrochemical tests on Aluminum 2060-T8E30 are performed to evaluate the susceptibility to EFC in two media: EXCO ASTM Standard solution: 4M NaCl 0.5M KNO3 and 0.1M HNO3 and a modified EXCO solution: 1M NaCl 0.25M NaNO3 0.033M AlCl3. The electrochemical tests performed include: Open Circuit Potential (OCP) Cyclic Potentiodynamic Polarization (CPP) Potentiostatic (PS) Galvanostatic (GS) and Electrochemical Impedance Spectroscopy (EIS) for quantitative results. Fluctuations of current and potential under free corroding conditions will be studied with OCP whereas CPP PS and GS are accelerated methods in which mechanisms of initiation and propagation of exfoliation corrosion will be analyzed. EIS tests are performed to characterize the substrate/electrolyte interface at steady state conditions; it can be used in the study of passive layer breakdown and localized attack as it can detect changes on the surface caused by the exfoliation process. Quantitative and qualitative analysis is included between surface morphology and transfer function (impedance) measurement.