Continuous and in-situ control of the galvanic process by spectrometers flow-cells.
In order to determine qualitative and quantitative chemical composition of liquids by the spectral way, in situ and on-line, both in by-pass mode as well as under flow injection analysis (FIA), the special flow cells are used. The column of flow liquid in the special cell is a photometer through a light beam transmitted via an optical fiber assembly from light source to a spectrometer, which is equipped with linear photodiode array as detector (Mallory, 2006). The chemical analysis is performed by automatic interpretation of the spectrograms that the specific absorption wavelength values identify the chemical species present in solution and the peak height is converted into concentration values(Kaim, 2008), Gutt, 2007). Such cells can be used in electrodepositing to determine continuously the concentration of galvanic electrolyte (Gutt, 2010); with the aim of automatic adjustment for the components in galvanic bath concentration without the possibility to determine the current and energy efficiency, without the possibility to determine the material and energy balance and without possibility to determine the process productivity according to specific working parameters (Gutt, 2010).
In the Instrumental Analysis Laboratory of the Faculty of Food Engineering Suceava, a flow cell was developed, built and tested figure 1, figure 2 and figure 3 which allows the qualitative and quantitative evaluation of the electrolyte by spectrophotometry, and achieving the materials and energy balance and the productivity calculation.
[FIGURE 1 OMITTED]
The experimental mode with electrochemical cell is as follows:
1. The galvanic deposition using a reserve of the electrolyte having the same composition as the industrial electrolyte and using same electrical working parameters (voltage and current density)--determines in time the evolution of the composition and concentration electrolyte for galvanic bath and at the same time by conducting the qualitative non-destructive measurements (brightness, thickness, uniformity of metal distribution, microscopic structure, roughness, etc.). The material and energy balance, current efficiency and productivity of industrial galvanic process are calculated with the values obtained and between parameters of work using and the quality galvanic deposit set correlations.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
2. The galvanic deposition in parallel with industrial cell using the same electrical parameters of working (voltage and current density), and the addition of other substances into the cell by flow injection analysis (FIA) method, the effect of nature and concentration additives on galvanic deposit quality are studied. For this purpose the cell electrolyte circuit is interrupted at regular intervals after that the cathode is removed and studied by specific measurements. These measurements reveal the influence of nature and concentration additives (brightening agents, wetting agents, leveling agents, buffering substances, et. al.).
3. The galvanic cell in parallel with the industrial cell using the same electrical parameters of working (voltage and current density), but using different flow rates of galvanic electrolyte, the values showing the influence of convection forced intensity on quantitative and qualitative parameters of deposition are obtained.
4. The galvanic cell in parallel with the industrial cell using the other electrical parameters of working (voltage and current density)--the amount of electrolyte taken through by-pass circuit is extremely small compared to the amount of electrolyte in the industrial bath which allows the work with other process parameters in cell than those in industrial cell. The conclusions obtained are used to optimize the industrial process.
3. RESULTS AND DISCUSSION
The use of the flow cell described above made automatically the registration of molecular absorption spectra for the flow electrolyte on three nickel deposits: I--freshly prepared electrolyte, II, III--electrolyte reused, in the sense that it was used in a second, third deposition respectively, the first electrolyte after deposition ceased, Figure 4.
For the three types of electrolytes, the developments of optical absorbance versus time using 1 experimental mode were followed. The determination results are illustrated in Figure 5, and in the same figure the regression equations are represented and the correlation coefficient describing the experimental changes as well.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
For the freshly prepared electrolyte used in the electroplating nickel deposit by the development of absorbance represented in figure 4, a microscopic structure on electron microscope (SEM) at magnification order M = 15.000X, figure 7, was performed.
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
By the galvanic flow cell above described, an important tool of the qualitative and quantitative investigation for the processes of galvanic metal deposition has been achieved; the cell working to by-pass with an industrial galvanizing bath, without affecting its good functioning. By disconnecting the power source at the two electrodes of galvanic cell it turns into a spectrophotometric flow cell in by-pass mode that allows continuous, on-line and in-situ measurement of galvanic electrolyte composition and concentration in industrial bath. The flow electrolyte changing trough cell allows the study of forced convection effect of electrolyte flow on the quality and quantity galvanic deposit. The cell has a simple construction, easy to clean, it has low cost price and it can be used outside galvanic processes and to study other electrochemical processes such as: electrochemical corrosion, electrorefining, dimensional controlled anodic processing.
Gutt G.,Gutt S., (2010) Messung und Bestimmung wichtiger Grossen und Indikatoren bei galvanischen Prozessen, Galvanotechnik, 2, Eugen Leuze Verlag, Saulgau, 268-272
Gutt S., Gutt G., (2010) Messeinrichtung fur wichtige Grossen und Indikatoren bei galvanischen Prozessen Galvanotechnik, 4, Eugen Leuze Verlag, Saulgau, 741-744
Gutt S., Gutt G., (2009), Analizor optic electrochimic, (Roumanian), Patent RO.122.611/2007, OSIM Bucuresti
Kaim, W., & Klein, A., (2008). Spectroelectrochemistry, Royal Society of Chemistry, Thomas Graham House, Cambridge, 124-127
Mallory, G.O., & Hajdu, B., (2006), J. Ectroless Plating: Fundamentals and Applications, Noyes Publications, New York, 169-193
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|Author:||Gutt, Sonia; Gutt, Gheorghe; Poroch-Seritan, Maria|
|Publication:||Annals of DAAAM & Proceedings|
|Date:||Jan 1, 2010|
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