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1

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A kinetic and electrochemical study of the zincate immersion process for aluminium (1995)

Robertson, S. G. ; Ritchie, I. M. ; Druskovich, D. M.

Springer

Journal of applied electrochemistry 25 (1995), S. 659-666

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ISSN: 1572-8838

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology

Notes: Abstract To plate aluminium, its surface is often first coated with a thin layer of zinc which is formed by immersion in an alkaline zincate solution. This paper describes a kinetic and electrochemical study of the zincate immersion reaction. Using an aluminium sample in the form of a rotating disc, the effects of varying the zinc concentration (0.01–0.5 m), disc rotation speed (66–1380 rpm), temperature (5–72°C), and sodium hydroxide concentration (1.5–9.0 m) on the kinetics were investigated. It was found that the reaction was usually first order. When the zincate concentration was 0.1 m, the reaction was chemically controlled with an activation energy of 35 ± 7 kJ mol−1. At high zincate concentrations, high disc rotation speeds and low sodium hydroxide concentrations, a thin film of zinc metal was formed on the aluminium surface, blocking the subsequent reaction. It was found that the most compact and adherent zinc films were formed at high zincate concentrations. This finding is consistent with industrial practice. These results are explained using mixed potential measurements and Evans' diagrams.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00241927

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2

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A capacitance study of the silver(I)/copper displacement reaction (1997)

RITCHIE, I. M. ; ROBERTSON, S. G.

Springer

Journal of applied electrochemistry 27 (1997), S. 59-63

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ISSN: 1572-8838

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology

Notes: Abstract Metal displacement (cementation) reactions are usually diffusion controlled and conform to first order kinetics. When a displacement reaction is carried out in a batch reactor, positive deviations from a first order rate plot are commonly observed once the deposit becomes sufficiently thick. It has been suggested that these rate enhancements are the result of changes in deposit structure resulting in increases in surface area. Another theory argues that the rate enhancements are due to turbulence associated with increasing roughness of the deposit. In this paper, an attempt is made to discriminate between these two possibilities by measuring the capacitance of a copper electrode immersed in a silver(I) solution. It was found that no anomalous capacitance changes were observed corresponding to the region in which rate increases were observed. This suggests that turbulence effects, rather than area effects, are responsible for the increased reaction rate. Capacitance measurements were also conducted for the reaction between silver(I) and copper in the presence of cyanide which caused the silver to deposit in a thin uniform layer on the copper surface, thus blocking the displacement reaction. It was found that the capacitance changed very little with time under these circumstances.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1026466916019

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The role of iron(iii) and tartrate in the zincate immersion process for plating aluminium (1997)

ROBERTSON, S. G. ; RITCHIE, I. M.

Springer

Journal of applied electrochemistry 27 (1997), S. 799-804

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ISSN: 1572-8838

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology

Notes: Abstract The zincate immersion process is a commercial process used to treat aluminium prior to electroplating. Superior zinc coatings are obtained through modifications to the original process. One such modification involves the addition of ferric chloride, complexed with potassium sodium tartrate, to the plating baths. This paper describes a detailed investigation into the function of these additives. It was found that the addition of tartrate alone did not significantly affect the rate of zinc deposition, the deposit morphology or the position of the aluminium or zinc polarization curves. This suggests that the role of tartrate is solely as a complexing agent to maintain iron (iii) in solution. In contrast to this, the addition of iron(iii)/tartrate had a marked effect on the reaction. It was found that iron(iii) functioned primarily by reducing the size of the zinc crystals as they formed. This produces a thinner and more compact zinc immersion coating.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018468627773

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Use of the bomb radiocarbon chronometer for age validation in the blue grenadier Macruronus novaezelandiae (1997)

Kalish, J. M. ; Johnston, J. M. ; Smith, D. C. ; [et al.]

Springer

Marine biology 128 (1997), S. 557-563

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ISSN: 1432-1793

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Accelerator mass-spectrometry was used to measure radiocarbon in the earliest formed portions of selected blue grenadier, Macruronus novaezelandiae, otoliths to provide a validation of fish-age estimates based on the quantification of opaque and translucent zones in otolith thin-sections. Δ14C data from blue grenadier otoliths were compared with previous estimates of Δ14C in seawater-dissolved inorganic carbon at similar latitutes, longitudes, and depths to link variation in otolith Δ14C to time. Minimum otolith Δ14C was −76.9 ± 7.7‰, indicative of pre-bomb radiocarbon levels below the surface mixed-layer at latitudes where juvenile blue grenadier are found. When plotted versus fish age estimated from otolith sections, the majority of the Δ14C data combined to define a curve reflecting the increase in bomb radiocarbon in temperate oceans of the Southern Hemisphere, indicating that age-estimation procedures based on otolith thin-sections are satisfactory for determining blue grenadier age. If otolith-section age estimates were correct, peak otolith Δ14C of 106.8 ± 7.9‰ occurred during the late 1960s, i.e. earlier than expected. This may be a manifestation of an increase in the mixed-layer depth associated with increased frequency of zonal westerly winds at this time.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002270050121

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Preliminary estimates of the age and growth of immature smooth oreo Pseudocyttus maculatus Gilchrist 1906 (Oreosomatidae) in the Falkland Islands region of the South Atlantic (1998)

George, M. J. A. ; Jackson, G. D. ; Green, C. P. ; [et al.]

Springer

Polar biology 19 (1998), S. 330-335

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ISSN: 1432-2056

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Sectioned otoliths were used to estimate the age of 29 specimens of the smooth oreo (Pseudocyttus maculatus Gilchrist 1906) from the Falkland Islands region of the South Atlantic. This represents the first ageing study of this species in this region of the world. All specimens were immature (sub-adults), the largest having a maximum total length of 347 mm. Growth increments were observed in sectioned otoliths and assumed to be annual in periodicity. The maximum age estimate of individuals in this study was 20 years and the form of somatic growth was similar to previous research on this species from Australian waters. The otolith microstructure consisted of an inner, mostly opaque zone with wide increments followed by an outer, mostly translucent zone with narrower increments. It is suggested that these zones correspond to the two growth phases in the life history of this species, namely the pelagic juvenile phase (opaque zone) and the demersal sub-adult/adult phase (translucent zone).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003000050254

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