Hydroxyapatite coating of AZ31 magnesium alloy by a solution treatment and its corrosion behavior in NaCl solution

Sachiko Hiromoto, Masanari Tomozawa

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

Hydroxyapatite (HAp) coatings were formed directly on AZ31 magnesium alloy and pure Mg in a 250mmol/L C10H12N2O8Na2Ca aqueous solution of pH 8.9. Treatment time was varied from 2h to 6h. Crystal phase, morphology and composition of the coatings were investigated. Immersion and polarization tests in a 3.5wt.% NaCl solution were performed to examine the corrosion behavior of the HAp-coated specimens. The HAp coating of AZ31 with short treatment time had defects which decreased with an increase in treatment time. The HAp coatings of AZ31 consisted of an inner dense layer and an outer coarse layer in the similar manner for pure Mg. The inner layer on AZ31 was composed of dome-shape precipitates densely packed. The outer layer was composed of rod-like crystals growing from each dome in the radial direction. The (002) plane of HAp of inner layer and rod-like crystals roughly oriented to the substrate. Magnesium ion-release and corrosion current density were remarkably reduced with HAp coatings. Each of these values was on the same order of magnitude between HAp-coated AZ31 and pure Mg. The ion release from AZ31 slightly decreased with an increase in treatment time. The original inner dense layer of AZ31 remained after the immersion. It is suggested that the protectiveness of HAp coating relays on the inner layer and does not significantly depend on the kind of Mg substrate.

Original languageEnglish
Pages (from-to)4711-4719
Number of pages9
JournalSurface and Coatings Technology
Volume205
Issue number19
DOIs
Publication statusPublished - 2011 Jun 25
Externally publishedYes

Keywords

  • AZ31 magnesium alloy
  • Biomaterials
  • Calcium phosphate
  • Corrosion
  • Hydrothermal treatment

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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