Anode aluminium

Anode slimes Anodization Ano diz ed aluminium Anodizing Anodizingaluminum... 

Panel numbering on acrylic sheet or aluminium anodized plates may be fixed on the front and the rear of each vertical panel for quick identification of each panel section (Figure 13.1). 

Imoi, H., Saito, Y., Kobayashi, M. and Fujiyama, S., Pitting-corrosion-resistant Chromium Stainless Steel , Japan Kokai 7300, 221 (1973) C.A., 79, 22569a Sato, E., Tamura, T. and Okabe, T., Aluminium Anode for Cathodic Protection. 7 Pitting and Corrosion Potentials for Gallium in Sodium Chloride Solutions , Kinzoku Hyomen Gijutsu, 24, 82 (1973) C.A., T9, 12792d... 

Although aluminium is a base metal, it spontaneously forms a highly protective oxide film in most aqueous environments, i.e. it passivates. In consequence, it has a relatively noble corrosion potential and is then unable to act as an anode to steel. Low level mercury, indium or tin additions have been shown to be effective in lowering (i.e. making more negative) the potential of the aluminium they act as activators (depassivators). Each element has been shown to be more effective with the simultaneous addition of zinc . Zinc additions of up to 5% lower the anode operating potential, but above this level no benefit is gained . Below 0 9 7o zinc there is little influence on the performance of aluminium anodes . Table 10.10 lists a number of the more common commercial alloys. 

The great attraction of aluminium anodes is their very high capacity, over three times that of zinc. They are attractive from a cost point of view and... 

Aluminium anodes comprise essentially three generic types Al-Zn-In, Al-Zn-Hg and Al-Zn-Sn. Since Al-Zn-Sn alloys have largely been superseded, they will not be discussed further. Indium and mercury are added to aluminium to act as activators, i.e. to overcome the natural passivation of aluminium. Despite this, aluminium anodes are not suitable for low chloride environments which would lead to passivation. These anodes are therefore not used for land-based applications (although examples of use in environments such as swamps do exist). Similarly their use in low chloride aqueous environments such as estuaries must be viewed with caution. 

Aluminium anodes are less constant in their electrochemical characteristics than zinc. This presents no major problem provided the designer is aware of their properties. They suffer from reduced capacity and increased operating potential (and hence risk of passivation) with increasing temperatures above approximately 50°C (Fig. 10.14), decreasing salinity (Figs. 10.15 and 10.16) and decreasing operating current density (Fig. 10.17). 

New combined (or binary) alloy sacrificial anodes have been developed . An aluminium anode, for example, might have attached to it a short-life supplementary magnesium anode, or anodes, for quick polarisation of the structure. The overall reduction in structure current requirements is claimed to result in an anode weight saving of 35-50% . 

Klinghoffer, O. and Linder, B., A New High Performance Aluminium Anode Alloy with High Iron Content , Paper No. 59, Corrosion/87, San Francisco, USA, March (1987) Crundwell, R. F., Sacrificial Anodes — Old and New . In Cathodic Protection Theory and Practice, 2nd International Conference, Stratford upon Avon, June (1989)... 

Fig. 10.29 Protection of offshore marine oil-drilling rig. (o) With external zinc (or aluminium) anodes and (b) with impressed current using platinised titanium or platinised niobium. (Compare the large number of anodes used in (a) with the small number used in (b))...

In view of its position in the e.m.f. series ( °aj3+/ai = 166V (SHE)), aluminium would be expected to be rapidly attacked even by dilute solutions of relatively weak acids. In fact, the rate of chemical attack is slow, owing to the presence on the aluminium of a thin compact film of air-formed oxide. When a voltage is applied to an aluminium anode there is a sudden initial surge of current, as this film is ruptured, followed by a rapid fall to a lower, fairly steady value. It appears that this is due to the formation of a barrier-layer. Before the limiting thickness is reached, however, the solvent action of the electrolyte initiates a system of pores at weak points or discontinuities in the oxide barrier-layer. 

Typically, the electrodes are of lead dioxide on a titanium substrate in the form of horizontal perforated plates, usually 5-40 mm apart, depending on the conductivity of the liquid. A potential difference of 5-10 V may be applied to give current densities of the order of 100 A/m2. Frequently, the conductivity of the suspension itself is adequate, though it may be necessary to add ionic materials, such as sodium chloride or sulphuric acid. Electrode fouling can usually be prevented by periodically reversing the polarity of the electrodes. Occasionally, consumable iron or aluminium anodes may be used because the ions released into the suspension may then assist flocculation of the suspended solids. 

Arylalkenes [23] and alkenes with electron withdrawing substituents [24] can be bis-alkylated across the alkene bond by electrochemical reaction with dflialoal-kanes giving 3- to 6-membered carbocyclic products in good yields. ITie best reaction conditions use an undivided cell with a nickel cathode and a sacrificial aluminium anode in dimethylformamide or N-methylpyrrolidone containing a tetraalkylammonium salt. Anodically generated aluminium ions are essential for the reaction. 1,2-Disubstituted alkenes, regardless of their stereochemistry, are converted to the tranj-substituted cycloalkane. 

Similarly, an aluminium anode is anodically converted to Al+ which for example can reduce nitrosobenzene in the anode compartment 1591 ... 

Organometallics can be prepared by anodic generation of reactive metal ions. Alkylaluminium halides, R-A1-X2, are produced by electrolysis of alkyl halides in the presence of AIX3 at an aluminium anode. AlX is assumed to be the reactive intermediate, which inserts into the C—Hal bond to form product (Eq. (276) ). 

Electrochemical technique (also electrocoagulation) is a simple and efficient method for the treatment of drinkable water. Recent results reported by Part-hasarathy and Yang [54,55] have demonstrated that electrocoagulation (EC) using aluminium anodes is effective in defluoridation. In the EC cell, the aluminium electrodes sacrifice themselves to form aluminium ions first. Afterwards the aluminium ions are transformed into AI(OH)3 before being polymerized to Aln(OH)3n. The AI(OH)3 floe is believed to adsorb F strongly as illustrated by the equation. 

Figure 8.21 Schematic process diagram for chromic acid recovery and water reuse in the aluminium anodizing process...

With samples less than 5 mm in diameter, the flat sample holder depicted in Fig. 8.15B affords direct analyses provided the sample is nominally fiat. The holder is mounted to the end of the DIP and comprises a PTFE clamp assembly, support rods, boron nitride spacers and either stainless steel or aluminium anode orifice plates. The DIP is placed through the clamp assembly and the rf feedthrough is placed directly behind the sample (cathode), which locks it in place. The spacers separate the anode plate and the cathode in the same manner as the 0-ring seal in the rf-AES source design. The anode body in this case is the Ta ion volume enclosed by the anode plate and the ion exit orifice mounted to it the entire cell assembly is affixed to the commercial source cryo-cooling ring. 

Patermarakis, G. 2006. Aluminium anodizing in low acidity sulphate baths Growth mechanism and nanostructure of porous anodic films. Journal of Solid State Electrochemistry 10, 211-222. 

Tang Y, Lu L, Roesky HW, Wang L, Huang B (2004) The effect of zinc on the aluminium anode of the aluminium-air battery. J Power Sources 138 313-318... 

XPS analysis was performed with an SSX-100 model photoelectron spectrometer (FISONS) using monochromatized aluminium anode. The binding energy (BE) values were calculated with respect to Cls (BE of C-CH... 

Expts. Transition metal anode Aluminium anodic loss [mg] Anodic circulated charge in C Al Trans, metal Polymerization time [h] Converted ethylene [%1 Polymer yield [%I... 

It should be noted, that maximum forming voltage (Uf) for an aluminium anodic process in an aqueous sulfuric solution is 30 V [1]. Our investigations have showed that forming voltage for Al-Ti alloys can reach 90-100 V in the same electrolyte. This result is new because the forming voltage determines the size of a cell in the porous oxide [1]. 

In Germany, Hoppecke has developed and built several prototypes of aluminiiun/air batteries with alkaline electrolytes and cylindrical aluminium anodes. The rods of aluminium are continually fed through gaskets at a rate which is identical to the rate of their consumption [15]. 

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