Loading...

Investigation and Synthesis of Zn-Ni-Mn Three Cationic Electrophosphate Coating

Alimi, Zahra | 2018

772 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50872 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohamad
  7. Abstract:
  8. The purpose of this study was to create a three-cationic electro phosphate coating of zinc-nickel-manganese by cathodic method and to investigate the effect of operating variables on the properties of zinc-nickel-manganese tri-cationic electro phosphate coating. Hence, the effects of variables such as coating acidity, coating thickness, coating temperature, coating time and concentration of manganese were studied in the bath on the properties such as coating morphology, corrosion resistance, coating thickness. Coating morphology was characterized by scanning electron microscopy and corrosion resistance by polarization test. The pH values of 1.4, 1.8, 2 and 2.2 were selected, and the results of scanning electron microscopic images and corrosion resistance show that the optimum pH range were 1.8-2 and in this range the corrosion resistance reported about 2×10-7 A/cm2. The applied current density was selected in the range of 5 to 35 mA / cm2. The morphology changes from the shape of the needle by increasing the current density to 25 mA /cm2, and the porosity of the coating decreases. Temperature was observed in the range of 65 to 85 ºC. It was observed that coating morphology has a plate structure by increasing temperature. In fact by decreasing the porosity with increasing temperature, the corrosion resistant decreases from 7× 10-7 to 2 × 10-7 A/cm2. Manganese concentration was investigated at 0, 1 and 2 g/l. By increasing the concentration of manganese to 1 g/l, the corrosion rate decreased from 7× 10-7 to 2 × 10-7 A/cm2. Time coating was investigated for a period of 5 to 60 minutes. By evaluating and analyzing the results at different times, the appropriate time to get the desired and maximum thickness, is reached 20 minutes. The basis for choosing these optimal values is maximum corrosion resistance and morphology with free defects. After obtaining a bath with optimum conditions by cathodic method, tri-cationic electro phosphate coating by anodic treatment was investigated. It was observed that the corrosion and adhesion resistance of the paint to the coating is less than cathodic treatment. In the cathodic method, the corrosion resistance is much improved compared to the anodic method due to reducing the porosity of the coating, completing the structure and observing the structure of the plate. the corrosion rate in anodic treatment to cathodic one is 1 × 10-6 and 2× 10-7 A/cm2 respectively and it decreases significantly
  9. Keywords:
  10. Adhesion ; Electrophosphating ; Corrosion Resistance ; Zinc-Nickel Coat ; Scanning Electron Microscopy (SEM)

 Digital Object List

 Bookmark

No TOC