Heterogeneity in Commercial Coating Systems for Aerospace Applications

 

Secondary ion mass spectroscopic (SIMS) mapping of alodine-treated 2024-T3 showed that the coating contains small amounts of all of the major alloying elements (Fe, Cu, Mn, Mg) that are inhomogeneously distributed across the surface (Figures 1 and 2). A variety of surface analytical techniques were used to characterize bulk samples of intermetallic compound analogs given a cold alodine coating, as described above. Differences were observed in the surface films formed on Al2Cu and Al2CuMg samples. It was also shown that that the Cr concentration and distribution on intermetallic compounds is different from that on matrix regions.

The combination of dynamic SIMS and SIRMS revealed dissimilarities in the depth distribution of CCC components. The results support findings that the CCC is inhomogeneously distributed across the AA2024-T3 surface. Potassium appeared to form an insoluble salt on the CCC surface thus increasing heterogeneity.

 

References:
  1. "Spatially-Resolved Microchemical Analysis of Chromate Conversion Coated Aluminum Alloys and Constituent Intermetallic Particles", G. P. Halada, C. R. Clayton, M. J. Vasquez, and J. R. Kearns, M. W. Kendig, S. L. Jeanjaquet, G. G. Peterson, G. Shea McCarthy, G. L. Carr, G. P. Williams, and L. M. Miller, Critical Factors in Localized Corrosion III-In Honor of Jerome Kruger's 70th Birthday, R. G. Kelly P. M. Natishan, G. S. Frankel and R. C. Newman (Eds.) Proceedings Volume 98-17, p.139, The Electrochemical Society, Pennington, NJ

  2. "Spatially Resolved Microchemical Analysis of Chromate Conversion Coated AA2024-T3", M. Vasquez, J. R. Kearns, G. P. Halada and C. R. Clayton, Submitted to Surface and Interface Analysis (2001).

 

Materials Science Department June-2005