Fabrication of Electrochemically Deposited Zinc Rich Ni-Co-Zn Alloy Coatings Reinforced with Pyridine and Investigation of Their Anticorrosion Performance in Acidic Medium

The immense corrosion rate of NiCo alloy coatings is the main problem to use it as constructive material. A study was carried out to synthesize Zn rich Ni-Co-Zn alloy coatings prepared on mild steel substrate with and without addition of Pyridine in deposition medium to test the effect of pyridine addition on corrosion of deposited alloy coatings. Galvanostatic electrodeposition technique was used to deposit alloy coatings on to the mild steel substrate at a fix current density of ۴ mA/cm۲. All ۴ coatings prepared from ۴ different deposition baths showed excellent surface coverage on Mild steel substrate. The alloy coatings were characterized by SEM, EDAX and XRD. The SEM analysis revealed the presence of cauliflower shaped agglomerated particles which are asymmetrically distributed throughout the surface. The XRD analysis confirmed the formation of alloy which is crystalline in nature and having h Zn-Ni as predominant phase along with the hZn, ZnO and Co۳O۴ Crystalline phase in all the coatings. The strain of the coatings was calculated using Williamson-Hall Plot. The anticorrosive performance of Ni-Co-Zn alloy coatings prepared in absence and presence of pyridine from different deposition baths were compared by potentiodynamic polarization measurement using tafel plot. The pyridine acts as moderate corrosion inhibitor and enhanced the corrosion resistance of the coatings. The comparative analysis of coatings obtained from DB۱ and DB۳ showed the percentage inhibitor efficacy of ۳۶.۹۱% in ۰.۰۱ M HCl medium and ۳۶.۹۴% in ۰.۰۱ M H۲SO۴ medium. The inhibitor efficacy of coating obtained from DB۴ when compared with the coating obtained from DB۲, it is higher in HCl medium (۶۶.۴۸%) as compared to H۲SO۴ medium (۴۰.۴۲%).

Keywords:

Galvanostatic deposition , Corrosion inhibitor , anticorrosive coating , Corrosion protection