Dissertation > Industrial Technology > Chemical Industry > Electrochemical industries > Electroplating industry > A single metal plating

Electroless Ni-Pon the Bulk Nanocrystalline Ingot Iron

Author ZhangXia
Tutor HeRongHeng
School Northeastern University
Course Physical and chemical
Keywords bulk nanocrystalline ingot iron Ni-P plating crystallization corrosion resistance binding energy
CLC TQ153.1
Type Master's thesis
Year 2009
Downloads 4
Quotes 0
Download Dissertation

Bulk nanocrystalline ingot iron (BNII) was produced from conventional polycrystalline ingot iron (CPII) by the severe rolling technique.Electroless nickel-phosphorus (Ni-P) is a technique for solid surface treatment. It has been adopted as representative chemical plating and widely applied in industry. Electroless Ni-P using sodium hypophosphite as a reducing agent, therefore the nickel ion is reduced directly on the catalytic reducting surface of the substrate from Ni-plating solution, and phosphorus is co-deposited simultaneously. Thus chemical Ni-P plating is performed.In this paper, high phosphorus (Pwt% 11%-13%) amorphous plating was obtained by optimum Ni-P electrless plating process at high temperatures of 88℃The acidity of the plating solution was controlled as 4.4-4.5 in pH with a buffer solution. Characterization of nickel-phosphorus plating including the structure and morphology, porosity, hardness, bonding strength, and corrosion resistance properties was made by using scanning electron micrograph, X-ray diffraction analyzer, X-ray photoelectron spectroscopy, metallographic microscope, hardness tester, chi660c electrochemical workstation equipment, respectively. The deposition mechanism of electroless Ni-P on BNII and CPII was studied, and improvement of electroless Ni-P plating on BNII was expected.The experimental results indicated that the prepared Ni-P plating has excellent gloss smoothness, zero porosity, and nice binding force. The thickness of the Ni-P plating was 24±1μm. The hardness was increased from HV 506 at the very beginning of chemical plating to HV 936 after treating at 390℃for 1h. The structure of Ni-P plating is amorphous at room temperature. A crystallized structure with two-phase Ni and Ni3P could be formed at elevated temperatures. The crystallization temperature of the plating on BNII was 340℃, and the melting point was about 883℃. According to the Tafel polarization analysis,in 5% NaCl and in 0.5 mol/L HCl solutions, the corrosion potential Ecorr of BNII with the plating is 216 mV and 197 mV higher than that without plating, respectively; The corrosion potential Ecorr of CPII with the plating is 50 mV and 118 mV higher than that without plating, respectively; Meanwhile, corrosion current density icorr of BNII with the plating (1.303×10-5 A/cm2,4.215×10-5 A/cm2, respectively) are obviously lower than those of BNII without plating (1.303×10-5 A/cm2,1.326×10-4 A/cm2, respectively).According to the X-ray photoelectron spectroscopy, the binding energy of the earlier plating was increased in 0.9 eV for P 2p3; decreaded in 0.1 eV for Ni 2p3 and 0.3 eV for Ni 2p1; decreased in 0.2 eV for Fe 2p3 and 0.4 eV for Fe 2p1, respectively, by comparing the results obtained from BNII plating with those from CPII plating.

Related Dissertations
More Dissertations