Galvanic interaction

There are 18 coimections for the arrangement with all electrodes connected as illustrated in Fig. 12.3 however, the ZRA had only 12 channels, so that only 12 currents could be measured simultaneously. The measuring procedure adopted was to measure the currents from the 12 electrodes from the left, or the 12 electrodes from the right. A total of five tests were carried out. 

In addition to the arrangement with all electrodes connected as illustrated in Fig. 12.3, the electrical connections could also be made to separately measure the galvanic currents from the left-hand side couple (St Mg) or alternatively separately measure the galvanic currents associated with the right-hand side couple (Mg St). For these measurements, there were no electrical connections to the six right-hand side electrodes (RHS steel electrodes 1 to 6) for the St Mg couple or alternatively there were no electrical connections for the left steel electrodes 1 to 6 for the Mg St couple. In each case, all currents could be measured simultaneously as there were 12 electrodes and also 12 channels for the ZRA. The data are plotted as shown in Fig. 12.9. 

10 Comparison of the BEM model of non-interacting galvanic current (St Mg and Mg St) and linear addition of non-interacting 

The experimental result of linear superposition is a somewhat surprising outcome. The boundary conditions are non-linear as is clear from Fig. 12.6. Linear superposition normally operates in a linear system. In a non-linear system, a theoretical error of second order of deviation is introduced, although this may be a small error. 

The apparent linear-superposition of the experimental data and BEM model predictions is attributed to the fact that the amount of interaction is small, so that it is not possible to measure or discern any non-linear effects. 

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Corrosion of the fasteners occurred due to their galvanic interaction with passive stainless steel. Deterioration was rapid because of the unfavorable area ratio formed by the large areas of stainless steel and the small area of the fasteners, which was further reduced by the incomplete plastic covering overexposed fastener surfaces. 

The more severe metal loss adjacent to the brass nozzles is apparently due to a direct galvanic interaction between the aluminum ring and the brass nozzles. The type of exfoliation observed microscopically in corroded areas is consistent with galvanic attack. 

In the case of mineral-mineral interactions, a mineral with higher potential acts as a cathode, while a mineral with lower potential acts as an anode. For a multiple mineral/grinding media(steel)system. The galvanic interactions become more complex than the two-electrode systems. The galvanic reactions among multielectrode systems are also governed by the mixed potential principle as shown in an example of polarization curves involving pyrite, pyrrhotite and mild steel in Fig. 1.9 (Pozzo and Iwasaki, 1987). 

The presence of oxygen enhances the formation of the surface coating and depresses the flotation of pyrrhotite. It appears, therefore, that although the floatability of individual mineral may be controlled by pulp potential, the presence of several sulphide minerals, particularly when they are ground with steel media, leads to galvanic interaction among them and the alteration of certain mineral surfaces may be accelerated. Then the pulp potential dependence of their floatability may not follow those of individual mineral. 

Grinding is essential for the liberation of sulphide minerals in order to achieve effective flotation. The grinding process, however, may also have a various effects on the flotation separation because of the galvanic interactions among the grinding media and the different minerals due to the high redox activity of sulphide mineral and iron media as well as thio-reagents. 

The interfacial galvanic interactions of sulphide minerals in the grinding system are affected by hitting or erasing force resulting in the formation of... 

A mechanical electrochemical equipment and corrosive couple equipment were designed in order to study the electrochemical behavior of sulphide mineral surface and galvanic interaction based on the method used by Rneer (1997) as shown in Fig. 8.1 and Fig. 8.2, respectively. 

Moreover, due to the rise in the electrode potential difference galvanic interaction between galena, sphalerite and pyrite, it will further accelerate the oxidation of the sulphides. 

Yelloji Rao M. K. and Natarajan, K. A., 1988. Influence of galvanic interaction between chalcopyrite and some metallic materials on flotation. Minerals Engineering, 1(4) 281 - 294 Yelloji Rao M. K. and Natarajan, K. A., 1989a. Effect of electrochemical interactions among sulphide minerals and grinding medium on chalcopyrite flotation. Minerals Metallurgical Processing, 6(3) 146- 151... 

Mehta, A. P. and L. E. Murr. 1983. Fundamental studies of the contribution of galvanic interaction to acid-bacterial leaching of mixed metal sulfides. Hydrometallurgy 9 235-256. 

Galvanic Interaction Between Titanium Metal and Ions... 

The second observation is that with the addition of benzotri-azole (BTA) to a nitric acid slurry the polish rates of both titanium and tantalum appear to be unaffected by the presence of copper ions. The BTA appears to suppress the galvanic interaction between the metals. One possible explanation is that the BTA surrounds the copper ions in solution and prevents interaction with the barrier metal. In the BTA slurry, the high selectivity makes the barrier metal an effective polish stop. BTA slurries are discussed in more detail in Chapter 7. 

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