Metallic problems

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. 

Koch, W., Hertwig, R. H., 1998, Density Functional Theory Applications to Transition Metal Problems , in Encyclopedia of Computational Chemistry, Schleyer, P. v. R. (Editor-in-Chief), Wiley, Chichester. 

W.Salomons, U.Forstner, P.Mader. 1995. Heavy metal problems and solutions. Springer. 

W. Salomons, U. Forstner and P. Mader, in Heavy Metals, Problems and Solutions , Springer, Berlin, 1988. 

When aluminum-silicon (Al-Si) metallization was deposited on wafers by evaporation, wet chemical analysis was used to study the changes in concentrations of Al to Si in the single evaporating cup. Wet chemical analysis was also used to determine the uniformity of silicon in aluminum and the evaporation patterns on the wafers in a rotating evaporator. The results revealed an accumulation of silicon in the cup and clearly showed the total lack of uniformity within a wafer and from wafer to wafer. The study showed why metallization problems were occurring and how to stop them. 

Elgersma, F., Schinkel, J.N., and Weijnen, M.P.C., Improving environmental performance of a primary lead and zinc smelter, in Heavy Metals Problems and Solutions, Salomons, W., Forstner, U., and Mader, P., Eds., Springer-Verlag, Berlin, 1995, p. 193. 

Stoewsand GS. 1980. Trace metal problems with industrial waste materials applied to vegetable producing soils. In Graham H.D., ed. The Safety of Foods. 2nd ed. Westport, CT AVI Publishing Co., Inc, 423-443... 

Forstner U, and Mader P, eds. Heavy metals. Problems and solutions, pp. 19—31. Springer-Verlag, Berlin. 

Limitation in the introduced amount of fines 7-8 kg/tonne metal Problem of extinction of flame... 

Cation hydrolysis can be of particular importance in modeling natural water systems with trace metal content and when attempting to avoid or cause hydrolytic precipitation of metals. Problems arise in that the true nature of many of the complexes resulting from cation hydrolysis are not known due to the tendency towards polynuclear species, that is complexes containing multiple metal ions, and the difficulty in their experimental determination. For example, Baes and Mesmer (5) note that chromic ion, Cr , reacts in water to form CrOH, CrfOH) and Cr(OH)iT ions. The aqueous molecule Cr(0H>3 is also likely to be present. Other complexes forming may be Cr COH) and CrsfOH). ... 

Basis Sets Correlation Consistent Sets Coupled-cluster Theory Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Density Functional Theory Applications to Transition Metal Problems G2 Theory Metal Complexes MpUer-Plesset Perturbation Theory Transition Metal Chemistry Transition Metals Applications. 

CSM = continuum solvation model COSMO = conductorlike screening model COSMO-RS = generalization of COSMO to real solvents QC = quantum chemical PCM = polarizable continuum model SAS = solvent accessible surface SES = solvent excluding surface NPPA = average number of segments per full atom vdW = van der Waals, VWN = Vosko-Wilk-Nusair functional (see Density Functional Theory Applications to Transition Metal Problems). 

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