Cobalt cleaning surface

Figure 9. Correction of H2S break-through times to clean surfaces 3.6 grams of cobalt molybdate catalyst, 54 mm. deep, 6.6 liters of H2 per hour...

Pretreatment is necessary to achieve a clean surface on the piece to be coated. To remove fat, oxides, and other impurities from the surface, defatting, etching, and descaling operations are carried out, which are then generally followed by a precoating step. In the case of aluminum plating, a prelayer of nickel, cobalt or iron or alloys of these metals (0.5-2 pm) is applied. Each treatment step is followed by one or more rounds of washing and conducted in such a manner as to minimize loss and to recycle valuable material [28, 29, 33, 127]. 

Atomic C and O are yielded by the dissociation of CO in FTS, the C adsorption on Co surfaces is crucial for this reaction. As listed in Table 2, the adsorption of C on most Co models is much stronger than the adsorption of H and O. Weststrate et al. made a systematic investigation on the C adsorption on Co surfaces. The experimental results indicated that atomic carbon weakened the adsorption of CO and H2, whereas a saturated (reconstructed) atomic carbon-covered surface can still adsorb 60% of the CO and H compared to the clean surface. Thus, a high coverage of atomic carbon may not be a strong poison to FT cobalt catalysts. In other words, FTS on Co catalysts is feasible in spite of the strong adsorption of C atoms on Co surfaces. 

Metals in the platinum family are recognized for their ability to promote combustion at lowtemperatures. Other catalysts include various oxides of copper, chromium, vanadium, nickel, and cobalt. These catalysts are subject to poisoning, particularly from halogens, halogen and sulfur compounds, zinc, arsenic, lead, mercury, and particulates. It is therefore important that catalyst surfaces be clean and active to ensure optimum performance. 

The surface properties of these nano-objects match those of metal nano crystals prepared in ultrahigh vacuum, for example the C - O stretch of adsorbed carbon monoxide or the magnetic properties of cobalt particles embedded in PVP. This demonstrates the clean character of the surface of these particles and its availabihty for reactivity studies. 

Polished nickel or cobalt plates were mounted in cylindrical graphite forms (11 mm inner diameter), rapidly heated up to about 450 °C and then filled with a molten flux (-475 °C) consisting of the eutectic mixture 82 mass % ZnCl2 - 18 mass % NaCl. After 60 s holding the plates under the flux for cleaning their surfaces from possible contamination, the forms... 

As has already been emphasised in connection with the electrodeposition of cobalt, it is essential that certain well-defined rules be adhered to, otherwise the deposited metal yields disappointing results. Thus the surfaces to be coated must be scrupulously clean, otherwise the nickel will flake off. A similar result accrues if the deposit is too thick, whilst if too feeble a current has been employed in the bath the deposited metal is too brittle, and tends to rub off during subsequent polishing. 

Permanent anodes are used in the electrowinning of base metals such as copper, nickel, cobalt, and zinc. The only function of the anode is to transfer electrons from the electrolyte to the external circuit. The usual reactions on the anode surface are oxygen evolution in sulfate electrolytes and chlorine evolution in chloride electrolytes. The permanent anodes have the disadvantages of maintenance costs to clean the... 

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