Header menu link for other important links
X
Corrosion resistance of electrodeposited Ni-B and Ni-B-Si3N4 composite coatings
Suresh Krishnamoorthy Seshadri
Published in
2009
Volume: 480
   
Issue: 2
Pages: 765 - 770
Abstract
Corrosion resistance of electrodeposited (ED) and electroless (EL) composite coatings have been a debatable issue in the published literature. The present paper aims to compare the corrosion resistance of ED Ni-B-Si3N4 composite coating with its plain counter part. The ED Ni-B coatings were prepared using Watt's nickel bath modified with the addition of dimethylamine borane and the ED Ni-B-Si3N4 composite coatings were prepared using the same bath in which Si3N4 particles (mean diameter: 0.80 μm) were dispersed in it. The structural and morphological characteristics of ED Ni-B and Ni-B-Si3N4 composite coatings were determined using X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The corrosion resistances of ED Ni-B and Ni-B-Si3N4 composite coatings, both in as-plated and heat treated conditions, in 3.5% NaCl, were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The study reveals that the extent of shift in corrosion potential (Ecorr) towards the noble direction, decrease in corrosion current density (icorr), increase in charge transfer resistance (Rct) and decrease in double layer capacitance (Cdl) values with the incorporation of Si3N4 particles in the ED Ni-B matrix is not appreciable, both in as-plated and heat-treated conditions. The occurrence of the second phase angle maximum suggests penetration of the electrolyte via the pores/micro-pores in these coating to create another interface, namely, the electrolyte/substrate. Unlike the nanosized particles, the micron size Si3N4 particles (mean diameter: 0.80 μm) used in this study is not capable of completely filling all the pores in the coating and allowed diffusion of chloride ions along the interface. The marginal improvement in corrosion resistance observed for ED Ni-B-Si3N4 composite coatings compared to its plain counterpart could have resulted from the decrease in effective metallic area prone to corrosion. © 2009 Elsevier B.V. All rights reserved.
About the journal
JournalJournal of Alloys and Compounds
ISSN09258388
Open AccessNo
Concepts (36)
  •  related image
    3.5%NACL
  •  related image
    Charge transfer resistance
  •  related image
    Chloride ions
  •  related image
    CORROSION CURRENT DENSITIES
  •  related image
    Corrosion potentials
  •  related image
    DIMETHYLAMINE BORANE
  •  related image
    Double-layer capacitance
  •  related image
    Electrochemical reactions
  •  related image
    Electroless
  •  related image
    Heat treated condition
  •  related image
    Matrix
  •  related image
    Mean diameter
  •  related image
    MICRON SIZE
  •  related image
    Morphological characteristic
  •  related image
    Nano-sized particles
  •  related image
    NANOFABRICATIONS
  •  related image
    Second phase
  •  related image
    SEM
  •  related image
    SURFACES AND INTERFACES
  •  related image
    Charge transfer
  •  related image
    Corrosion resistance
  •  related image
    Diffraction
  •  related image
    Diffusion coatings
  •  related image
    Electrochemical corrosion
  •  related image
    Electrochemical impedance spectroscopy
  •  related image
    Electrodeposition
  •  related image
    Ion exchange
  •  related image
    Nanostructures
  •  related image
    Nickel
  •  related image
    Phase interfaces
  •  related image
    Scanning electron microscopy
  •  related image
    Silicon
  •  related image
    Sodium chloride
  •  related image
    X ray diffraction
  •  related image
    X ray diffraction analysis
  •  related image
    Composite coatings