An Investigation on Effects of Electroless Nickel- Phosphorous Coating and Heat Treatment on Corrosion Resistance of Carbon Steel

  • سال انتشار: 1388
  • محل انتشار: دومین کنفرانس بین المللی رنگ و پوشش خودرویی
  • کد COI اختصاصی: ICAPC02_012
  • زبان مقاله: انگلیسی
  • تعداد مشاهده: 1881
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نویسندگان

T Rabizade

MSc Student

S. R. Allahkaram

Associate Professor and Member of Center of Excellence in High Performance Ultra Fine Materials

A. Zarebidak

PhD Student School of Metallurgy and Materials Engineering, University College of Engineering

چکیده

The autocatalytic (electroless) deposition of Ni–P coating is a well-known commercial process that has found numerous applications because of its excellent anticorrosive, wear, magnetic, solderable properties, etc. It is a barrier coating,protecting the substrate by sealing it off from the corrosive environments, rather than by sacrificial action. In the present investigation Ni–P nano-crystalline coatings were prepared by electroless deposition from electroless nickel bath with sodium hypophosphite as reducing agent. Post-deposition vacuum heat treatment effects on coating properties were studied. X-ray diffractometry (XRD), scanning electron microscopy (SEM),energy dispersive analytical X-ray (EDAX), potentiodynamic polarization were utilized to analyse the temperature dependence of the microstructure, composition, mechanical and corrosion properties of the coatings. X-ray diffraction (XRD) studies indicated that the as-plated deposits were nano-crystalline, i.e. 39 nm. The heat treatment of the coatings increased their grain size and a mixture of polycrystalline Ni and Ni3P alloy occurred at around 400°C. The highest microhardness was achieved for the samples annealed at 600°C for 15 min because of formation of an inter-diffusional layer. Corrosion resistance of the films was evaluated in 3.5% sodium chloride solution via potentiodynamic polarization and electrochemical impedance (EIS) methods. Lower corrosion current density values were obtained for the coatings heat treated at 400°C for 1hour.

کلیدواژه ها

Electroless plating; Ni-P coating; Nano-crystalline coating; Vacuum heat treatment; Micro-hardness; X-ray diffraction; Corrosion resistance

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