126
M. Scott and M. Moats
was dipped in a 0.25% v/v nitric solution for one minute and then rinsed again with
D.I. water. Finally, the coated plate was dried with hot air to avoid water spots.
Physical Characterization
Following the Hull cell test, the plate was visually inspected. The appearance was
graded using the following terms burnt (blackish in color), matte (gray and nonreflective), white, shiny (gray, reflective, sparkly), or no plating. These appearances
were assigned to various areas of the deposit which were correlated to current density
using the two-amp scale on a standard Hull cell ruler. The zinc coated plates were
sheared to create samples with known current density ranges for further examination.
X-ray diffraction (XRD) was performing using a Philips Panalytical X’Pert Pro
Multipurpose Diffractometer to identify the preferred crystal orientation for samples
plated at 170–260 A/m
2 . The measurements were taken using Cu K-alpha radiation
with an angle range in 2 θ of 50–90º and scanning rate of 3º per minute.
Zinc coatings plated at 170 A/m
2 were characterized by scanning electron
microscopy (SEM) to observe the deposit morphology. An Aspex Pica 1020 scanning
electron microscope was used with 20 kV bias and 34 µA emission current.
Results and Discussion
While other researchers [14–19] have examined the effects of additives on the alkaline zincate plating, this project focused on a unique bath chemistry as the zinc
concentration (30–40 g/L) and sodium hydroxide concentration (210–220 g/L) are
significantly higher than standard baths in both zinc and NaOH.
To understand the role of each additive, synthetic solutions with constant initial
zinc and NaOH concentrations of 37.5 g/L and 210 g/L, respectively, were studied
with various additive additions. The resulting zinc coatings produced in the Hull cell
were characterized visually, with XRD and microscopically with SEM.
Hull Cell
The results of the visual characterization are presented in Table 2. The addition of
individual additives or combinations of additives did not produce any areas with
the desired mirror finish. At high current densities, the coating usually had a burnt
appearance. At lower current density, the coating generally had a matte appearance.
The surfaces that were closest to the desired appearance were categorized as
white. These surfaces were bright but not completely reflective. As expected, plating
without additives did not produce any white areas. Several plating conditions yielded
M. Scott and M. Moats
was dipped in a 0.25% v/v nitric solution for one minute and then rinsed again with
D.I. water. Finally, the coated plate was dried with hot air to avoid water spots.
Physical Characterization
Following the Hull cell test, the plate was visually inspected. The appearance was
graded using the following terms burnt (blackish in color), matte (gray and nonreflective), white, shiny (gray, reflective, sparkly), or no plating. These appearances
were assigned to various areas of the deposit which were correlated to current density
using the two-amp scale on a standard Hull cell ruler. The zinc coated plates were
sheared to create samples with known current density ranges for further examination.
X-ray diffraction (XRD) was performing using a Philips Panalytical X’Pert Pro
Multipurpose Diffractometer to identify the preferred crystal orientation for samples
plated at 170–260 A/m
2 . The measurements were taken using Cu K-alpha radiation
with an angle range in 2 θ of 50–90º and scanning rate of 3º per minute.
Zinc coatings plated at 170 A/m
2 were characterized by scanning electron
microscopy (SEM) to observe the deposit morphology. An Aspex Pica 1020 scanning
electron microscope was used with 20 kV bias and 34 µA emission current.
Results and Discussion
While other researchers [14–19] have examined the effects of additives on the alkaline zincate plating, this project focused on a unique bath chemistry as the zinc
concentration (30–40 g/L) and sodium hydroxide concentration (210–220 g/L) are
significantly higher than standard baths in both zinc and NaOH.
To understand the role of each additive, synthetic solutions with constant initial
zinc and NaOH concentrations of 37.5 g/L and 210 g/L, respectively, were studied
with various additive additions. The resulting zinc coatings produced in the Hull cell
were characterized visually, with XRD and microscopically with SEM.
Hull Cell
The results of the visual characterization are presented in Table 2. The addition of
individual additives or combinations of additives did not produce any areas with
the desired mirror finish. At high current densities, the coating usually had a burnt
appearance. At lower current density, the coating generally had a matte appearance.
The surfaces that were closest to the desired appearance were categorized as
white. These surfaces were bright but not completely reflective. As expected, plating
without additives did not produce any white areas. Several plating conditions yielded