Aluminium surfaces

Emissivity Table 15.5 shows the total heat emissivity of various aluminium surfaces, as a percentage of that of a black body. The figures have been recalculated from the data of Hase. The emissivity of anodised aluminium rises rapidly with film thickness up to 3 fim after which the rate of increase diminishes. 

Relative heat emissivity of various aluminium surfaces... 

Reflectivity The total and specular reflectivities of an anodised aluminium surface are controlled by both the condition of the metal surface, polished... 

Treverton, J. A. and Davies N. C. XPS Studies of a Ferricyanide Accelerated chromate Paint PretreatmenI Film on an Aluminium Surface , Surf. Interfacial Ana ., 3, 194-200 (1981)... 

Dissimilar metals in the same system Because of the specific action of many inhibitors towards particular metals, problems arise in systems containing more than one metal. In the majority of cases these problems can be overcome by the choice of a formulation incorporating inhibitors for the protection of each of the metals involved. With this procedure it is necessary not only to maintain an adequate concentration of each of the inhibitors but also to ensure that they are present in the correct proportion. This is because of two effects firstly, failure to inhibit the corrosion of one metal may intensify the attack on the other metal the best example of this is with aluminium and copper in the same system, and failure to inhibit copper corrosion — usually achieved with sodium mercaptobenzothiazole or benzotriazole—can lead to increased corrosion of the aluminium as a result of deposition of copper from copper ions in solution on to the aluminium surface. Secondly, an inhibitor of the corrosion of one metal may actually intensify the corrosion of another metal. Thus, benzoate is usually used to prevent the corrosion of soldered joints by nitrite inhibitor added to protect cast iron in the same system. A benzoate nitrite ratio of greater than 7 1 is necessary in these cases. 

That carbon monoxide could be oxidised in a facile reaction at cryogenic temperature (100 K) was first established in 1987 by XPS at an aluminium surface.21 The participation of reactive oxygen transients O 1 (s) was central to the mechanism proposed, whereas the chemisorbed oxide O2 state present at 295 K was unreactive. This provided a further impetus for the transient concept that was suggested for the mechanism of the oxidation of ammonia at a magnesium surface (see Chapter 2). Of particular relevance, and of crucial significance, was Ertl s observation by STM in 1992 that oxygen chemisorption at Al(lll) resulted in kinetically hot adatoms (Figures 4.1 and 4.7). 

The Natural Passivation and Corrosion of Metals and Alloys XPS studies of the air-formed natural passive layer on aluminium surfaces have identified a number of hydroxides as well as alumina (Barr, 1977). The oxidation of pure iron and of stainless steels and other iron alloys have also been extensively... 

Cohen et al. [361] studied, amongst other things, the influence of heat on monolayers of OTS and of arachidic acid adsorbed on surfaces of aluminium oxide formed on aluminium surfaces. They used wetting studies and infrared spectroscopy and concluded that, whereas arachidic acid layers deteriorated in an irreversible manner at about 100°C, OTS layers survived intact to about 140°C. This result is attributed by these authors to polymerisation of the latter material but could also be due to a rather different bonding mechanism between the organic material and the aluminium oxide. 

Coated E-glass slide surface. (A) Positive ions. As shown in Fig. 3 and Table 3, the major components on the heat-cleaned surface are Si (m/z = 28), A1 (m/z = 27), and Ca (m/z = 40). However, from Table 4 it can be seen that the aluminium surface concentration after treatment with HAPS was still very intense and increased after extraction with warm and hot water. These results are consistent with the XPS results shown in Figs 1 and 2, and are further indicative of aluminium becoming an integral part of the surface coating. Moreover, for the HAPS deposited from deionized water onto silver foil (99.99%), the peak at... 

Aluminium sheet If a drop of mercury(I) nitrate is placed on a clean aluminium surface, aluminium amalgam is formed and aluminium ions pass into solution ... 

Remarkably uniform MgO smoke was prepared by Coulomb and Vilches (1984) by burning magnesium ribbons in dry OjAi mixtures. The MgO particles were collected in die form of a coating on a clean aluminium surface and were subjected to heat treatment (at c. 950°C and pressures < 10 6 mbar). The specific surface area of the final MgO(l 0 0) powder was c. 8 m2 g-1 so that it was not difficult to undertake accurate physisorption measurements and also neutron scattering experiments. 

Apart from simple corrosive attack on a metal surface, Gabel reported a more specific situation leading to corrosion. This occurred when a dry-film-lubricated metal surface was in contact with an unlubricated anodized aluminium surface. Laboratory investigation at 95% relative humidity and 49°C (120°F) confirmed that in this situation the corrosion resistance of the anodized aluminium was reduced from 1100 hours to fewer than 200 hours. It was not clear whether dissimilar metals were involved, but the occurrence suggested that corrosion might be due to the development of an external potential in the presence of an electrolyte. 

Corrosion rate on steel or aluminium surfaces exceeding 6.25 mm per year at a test temperature of 55 °C. 

Does it corrode on steel or aluminium surfaces at a rate exceeding 6.25 mm/year ... 

In the laser induced photopolymerisation of methyl methacrylate on an aluminium surface the kinetics have been found to be controlled... 

In this Chapter, we focus on alkali-aluminum surface alloys where the geometrical structure has been determined in detail. As can be seen from Table 1, which contains a list of the adsorbed phases formed by adsorption of alkali metals on aluminium surfaces, this limitation is not a serious restriction, since studies exist for a quite a number of low index aluminum surfaces and alkali metals. Although most of the structures of the phases listed in Table 1 have been determined by low energy electron diffraction (LEED), the crucial, first observation of substitutional adsorption for alkali-aluminium systems was made in a combined surface extended x-ray fine structure (SEXAFS) and density functional theory (DFT) study of the Al(l 11)—(v 3 x 3)7 30°—Na phase formed by adsorption of 1/3 ML Na at room temperature by Schmalz et al [7] in 1991. The structure of the Al(lll)-(4 x 4)—Na phase was also determined by SEXAFS. 

Surface alloys formed by adsorption of alkali metals on aluminium surfaces. 

Figure 5.16. MAS NMR spectra of anodic films formed on aluminium surfaces in different acid electrolytes. Adapted from Faman et al. (1989).

Mori, S., Suginoya, M. and Tamai, I. (1982) Chemisorption of organic compounds on a clean aluminium surface prepared by cutting under high vacuum, ASLE Trans. 25 261-266. 

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