New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

L. Toro, A. A. Zuleta, E. Correa, D. Calderón, Y. Galindez, J. Calderón, P. Chacón, A. Valencia-Escobar, F. Echeverría E

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

In this work, anodic oxide layers on the surface of an AZ31 magnesium alloy were obtained by plasma electrolytic oxidation (PEO) process under low frequency pulsed current. For this, electrolytical solutions containing hexamethylenetetramine and sodium fluoride were used. The morphology and chemical composition of formed coatings were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Also, salt spray test, hydrogen evolution and electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were conducted in order to study the corrosion behavior of the coated samples. It was found that the use of low frequency pulsed current for the PEO process reduces the film porosity and increases its thickness, compared with PEO films obtained by continuous anodization. The effect of the pulsed current signal was also analyzed for a two steps PEO process, observing changes in the morphological characteristics of the coatings which allow a better corrosion according electrochemical tests (short term corrosion measurements). However, long term tests results as hydrogen evolution and salt spray tests, indicated the opposite. Both the film porosity and thickness were affected by either the pulsing of the current or the use of a two-step process.

Original languageEnglish
Article number016539
JournalMaterials Research Express
Volume7
Issue number1
DOIs
StatePublished - 1 Jan 2020

Keywords

  • anodizing
  • corrosion
  • Mg-Al-Zn alloys
  • plasma electrolytic oxidation
  • salt fog test

Fingerprint Dive into the research topics of 'New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B'. Together they form a unique fingerprint.

Cite this