A Novel Organic Conversion Coating based on N-Benzoyl-N-Phenylhydroxylamine Chemistry for the Corrosion Protection of AA2024-T3

Xiaolei Guo, Belinda Hurley, Fan Yang, Rudolph Buchheit

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


This work demonstrates a novel organic conversion coating treatment on an AA2024-T3 substrate. The process is based on simple immersion in aqueous solutions containing an organic molecule, N-Benzoyl-N-phenylhydroxylamine (BPHA), after a hydrothermal oxide has been formed on the alloy surface. Potentiodynamic polarization results indicate that BPHA conversion coating outperforms coatings formed in the same concentration of other corrosion inhibitors, including NaVO3, Na2SiO3, CeCl3, and benzotriazole. BPHA coating also displays strong and persistent corrosion inhibition under ASTM B117 salt spray exposure conditions and static immersion testing. The cross-section of BPHA-coated substrate is prepared by focus ion beam-scanning (FIB), and analyzed by high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) coupled with energy dispersive spectroscopy (EDS), which show a thick surface film with a three-layer structure. Raman spectroscopy and XPS are used to examine the surface chemistry of BPHA-coated samples, both of which suggest the formation of a BPHA surface film, possibly stabilized by the keto-to-iminol conversion that made the BPHA molecule strongly nucleophilic. The formation of BPHA-metal oxide complex seems to be closely related to the excellent corrosion resistance of BPHA coating.

Original languageEnglish
Pages (from-to)197-207
Number of pages11
JournalElectrochimica Acta
StatePublished - Aug 20 2017

Bibliographical note

Funding Information:
Support for this project by the U.S. Department of Agriculture under Award number 2012-38202-19288 and The Ohio State University is gratefully acknowledged. Support from National Science Foundation under Grant No. 0639163 is also acknowledged for the purchase of the Raman microprobe system.

Publisher Copyright:
© 2017 Elsevier Ltd


  • N-Benzoyl-N-phenylhydroxylamine
  • conversion coating
  • corrosion
  • tautomerization

ASJC Scopus subject areas

  • Chemical Engineering (all)
  • Electrochemistry


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