Enhanced Protective and Mechanical Properties of Polypyrrole Coatings Modified by Silane/CoO Nanocomposite on AZ91 Mg Alloy in Chloride Media

Newly synthesized nanocomposite coatings containing polypyrrole (Ppy), silanes, and CoO nanoparticles (polypyrrole/silane/CoO nanocomposite) for magnesium alloy (AZ91) protection in 3.5% NaCl solution were investigated by electrochemical techniques and mechanical studies. Electrochemical impedance s...

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Bibliographic Details
Published in:Journal of bio- and tribo-corrosion 2021, Vol.7 (2), Article 46
Main Authors: Xavier, Joseph Raj, Beryl, J. Raja, Vinodhini, S. P., Janaki, G. Boomadevi
Format: Article
Language:English
Subjects:
Biomaterials
Charge transfer
Chemistry and Materials Science
Coatings
Corrosion
Corrosion and Coatings
Corrosion currents
Corrosion prevention
Corrosion products
Diffusion coating
Diffusion layers
Diffusion rate
Dissolution
Electrochemical impedance spectroscopy
Electrode polarization
Energy dispersive X ray analysis
Immersion
Ion diffusion
Magnesium
Magnesium alloys
Magnesium base alloys
Materials Science
Mechanical properties
Nanocomposites
Nanoparticles
Polypyrroles
Scanning electron microscopy
Silanes
Sodium chloride
Solid Mechanics
Submerging
Synthesis
Tribology
X ray analysis
X-ray diffraction
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Summary:Newly synthesized nanocomposite coatings containing polypyrrole (Ppy), silanes, and CoO nanoparticles (polypyrrole/silane/CoO nanocomposite) for magnesium alloy (AZ91) protection in 3.5% NaCl solution were investigated by electrochemical techniques and mechanical studies. Electrochemical impedance spectroscopic (EIS) analysis displayed a significant increase in the charge transfer ( R ct : 7516.67 kΩ cm 2 ) and coating resistances ( R c : 4825.32 kΩ cm 2 ) for Ppy/MES/CoO nanocomposite coating compared to polypyrrole coating ( R ct : 545.88 kΩ cm 2 and R c : 9.86 kΩ cm 2 ) at 80 days of immersion. Potentiodynamic polarisation studies exhibited a significant reduction in the corrosion current for the Ppy/silane/CoO nanocomposite. The passive layer formed by the studied nanocomposite prevented the diffusion of aggressive ions into the coating. The addition of silane functionalized CoO nanoparticles into the polypyrrole coating slowed down the diffusion of ions by forming an enclosed pathway. This resulted in charge transfer inhibition at the Mg alloy/electrolyte interface which suppressed the dissolution of Mg alloy. Scanning electrochemical microscopic (SECM) analysis confirmed the presence of the lowest corrosion current of 2.5 nA for Ppy/MES/CoO coated Mg alloy and a higher corrosion current of 13.6 nA for polypyrrole coating at 80 days immersion. Surface morphological studies of synthesized nanocomposite coatings were investigated by scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray diffraction (XRD) technique. SEM/EDX analysis displayed the formation of passive corrosion product layers that hindered the dissolution of magnesium alloy. The improved mechanical properties were noticed for the nanocomposite coatings containing silane-modified CoO nanoparticles and polypyrrole.
ISSN:2198-4220
2198-4239
DOI:10.1007/s40735-021-00479-7