128
M. Scott and M. Moats
XRD and SEM
To understand the visual observations, XRD and SEM were performed on the samples
produced from synthetic solutions. Sample XRD data from 170 to 260 A/m
2 and SEM
images from 260 A/m
2 are provided in Table 3 and Fig. 1, respectively. The XRD
data was interpreted using the nomenclature used by Mackinnon et al. [20].
The XRD data reveal that without additives, a basal zinc structure is produced
at 170 A/m
2 . This is confirmed in Fig. 1a where the expected hexagonal plates are
observed. The addition of 0.65 mL/L of booster did not change the structure as shown
in the XRD and SEM image (Fig. 1c); however, a 0.33 mL/L booster addition did
change the structure. Upon the addition of carrier, the structure and morphology
changed to yield primarily triangular growth and a nodular/bumpy surface (Fig. 1b).
The addition of 0.65 mL/L of leveler did not change the structure, but 1.3 mL/L did to
triangular, but the surface morphology revealed a variable appearance which might
be caused by the strong secondary vertical growth seen in the XRD data (Fig. 1d).
Carrier and booster additions produced a structure similar (Fig. 1e) to what only
carrier addition produced with the nodules being smaller. This is expected result of
the grain refining properties of the booster. When leveler and carrier were added, a
smooth triangular structure formed (Fig. 1f) with a few large nodules. Booster and
leveler additions created a mixed basal/triangular structure which caused a rough
faceted surface (Fig. 1g). Upon the addition of all three additives at appropriate
concentrations, the structure was more level causing a brighter deposit (Fig. 1h). The
structure and surface morphology did not change over the range of 30–40 g/L zinc.
The bright white finish general was produced when the XRD pattern indicates
a primary triangular growth with minimal basal growth. Additionally, the vertical
growth plane was detected at ~50% of the intensity of the triangular plane.
After consultation with our industrial partner, it was decided that the lack of a
mirror finish was perhaps caused by the additives not being allowed to age enough
in the Hull cell before current was applied. Based on industrial experience and the
SEM images, it was decided to pursue a combination of all three additives in later
trails with commercial bath samples.
Summary
This study provides zinc coating data for a unique zincate plating bath with high
zinc and caustic concentrations. The effects and interactions of commercial additives (carrier, booster, and leveler) were examined using a Hull cell. Coatings were
characterized using visual appearance, XRD and SEM.
Bright white deposits were produced at current densities of 170–420 A/m
2 . The
conditions that produced bright white deposits generally formed a zinc structure with
predominate (101) planes, minimal (002) planes and (100) planes with an intensity
~50% of the (101) planes.
M. Scott and M. Moats
XRD and SEM
To understand the visual observations, XRD and SEM were performed on the samples
produced from synthetic solutions. Sample XRD data from 170 to 260 A/m
2 and SEM
images from 260 A/m
2 are provided in Table 3 and Fig. 1, respectively. The XRD
data was interpreted using the nomenclature used by Mackinnon et al. [20].
The XRD data reveal that without additives, a basal zinc structure is produced
at 170 A/m
2 . This is confirmed in Fig. 1a where the expected hexagonal plates are
observed. The addition of 0.65 mL/L of booster did not change the structure as shown
in the XRD and SEM image (Fig. 1c); however, a 0.33 mL/L booster addition did
change the structure. Upon the addition of carrier, the structure and morphology
changed to yield primarily triangular growth and a nodular/bumpy surface (Fig. 1b).
The addition of 0.65 mL/L of leveler did not change the structure, but 1.3 mL/L did to
triangular, but the surface morphology revealed a variable appearance which might
be caused by the strong secondary vertical growth seen in the XRD data (Fig. 1d).
Carrier and booster additions produced a structure similar (Fig. 1e) to what only
carrier addition produced with the nodules being smaller. This is expected result of
the grain refining properties of the booster. When leveler and carrier were added, a
smooth triangular structure formed (Fig. 1f) with a few large nodules. Booster and
leveler additions created a mixed basal/triangular structure which caused a rough
faceted surface (Fig. 1g). Upon the addition of all three additives at appropriate
concentrations, the structure was more level causing a brighter deposit (Fig. 1h). The
structure and surface morphology did not change over the range of 30–40 g/L zinc.
The bright white finish general was produced when the XRD pattern indicates
a primary triangular growth with minimal basal growth. Additionally, the vertical
growth plane was detected at ~50% of the intensity of the triangular plane.
After consultation with our industrial partner, it was decided that the lack of a
mirror finish was perhaps caused by the additives not being allowed to age enough
in the Hull cell before current was applied. Based on industrial experience and the
SEM images, it was decided to pursue a combination of all three additives in later
trails with commercial bath samples.
Summary
This study provides zinc coating data for a unique zincate plating bath with high
zinc and caustic concentrations. The effects and interactions of commercial additives (carrier, booster, and leveler) were examined using a Hull cell. Coatings were
characterized using visual appearance, XRD and SEM.
Bright white deposits were produced at current densities of 170–420 A/m
2 . The
conditions that produced bright white deposits generally formed a zinc structure with
predominate (101) planes, minimal (002) planes and (100) planes with an intensity
~50% of the (101) planes.