Characterisation of phosphate coatings on zinc, zincnickel and mild steel by impedance measurements in dilute sodium phosphate solutions

Electrochemical and surface analytical study of the corrosion behavior of mild steel with cathodically produced zinc phosphate coating

“…In the model, R P is the polarization resistance, R PC is the resistance of the phosphate coating, C dl is the double layer capacity and C PC is the capacitance of the phosphate coating. The higher values for C dl , R P and R PC with immersion time correspond to a better protection performance of the phosphate coating, which is supported by Zn(OH) 2 . This means that a charge transfer is blocked at the pores and the active area is decreased.…”

“…EDX analyses demonstrate an increase in the Zn content (50 to 73 wt%), a light decrease in the oxygen content (20 to 15.5 wt%) and a complete disappearance of the phosphorus signal with time. Owing to the stoichiometric order of the ions, these findings indicate the transformation of the original hopeite layer first into Zn(OH) 2 and then into ZnO. The impedance spectra measured in the alkaline electrolyte are shown in Fig.…”

“…A possible explanation for this finding is that the oxygen reduction reaction preferentially takes place in the pores of the coating, leading to a local increase in the pH value (from pH 5.6 to pH 6.9). Hence, the hopeite layer is attacked by the alkaline electrolyte (see Section on Behavior in 0.1 M NaOH) and converted into Zn(OH) 2 . Starting from the pores, this underneath layer is laterally spread undermining the phosphate coating.…”

Investigation of Passive Film Properties and Pitting Resistance of AISI 316 in Aqueous Ethanoic Acid Containing Chloride Ions using Electrochemical Impedance Spectroscopy(EIS)

“…The most straightforward interpretation is to consider it as a dispersive capacitance of the double layer. [7,8]. It is thought to arise from a distribution of the relaxation times resulting from heterogeneities of microscopic level at oxide/electrolyte interface [6,9,10].…”

Siliconizing formation mechanism and its property by slurry pack cementation on electro-deposited nickel layer into copper matrix

“…Among these techniques, the pack cementation, a diffusion formation process, widely used to deposit high-temperature oxidation-and corrosion-resistance coatings on nickel-based superalloys and low-alloy steels [4] . In recent years, several intermetallic compound coatings have been developed and successfully employed to copper surface with minimal wear in sliding and good oxidation properties [5][6][7] .…”