Passivation metals

Pasefaen series See Balmer series, passivators See metal passivators. 

Concentrated nitric acid renders the metal passive , i.e. chemically unreactive, due to formation of a thin oxide surface film (which can be removed by scratching or heating in hydrogen). 

Metal passivation Metal pickling Metal powders Metal recovery... 

Condensate systems can be chemically treated to reduce metal corrosion. Treatment chemicals include neutralising amines, filming amines, and oxygen scavenger-metal passivators. 

The use of neutralising amines in conjunction with an oxygen scavenger—metal passivator improves corrosion control in two ways. First, because any acidic species present is neutralized and pH is increased, the condensate becomes less corrosive. Second, most oxygen scavenger—passivators react more rapidly at the mildly alkaline conditions maintained by the amine than at lower pH levels. For these reasons, this combination treatment is gaining wide acceptance, particularly for the treatment of condensate systems that are contaminated by oxygen. 

At high metals levels, the coking characteristics of a cracking catalyst can be greatly increased that is, the ratio of contaminant coke to catalytic coke can be quite high. The effect of the contaminant metals on the coke response is affected not only by the level of metals but also by the type of catalyst and the use of a metals passivator. Catalysts, which contain effective metals traps to inhibit the contaminant effects, do produce much less contaminant coke than catalyst without metal traps. 

Another approach used to reduce the harmful effects of heavy metals in petroleum residues is metal passivation. In this process an oil-soluble treating agent containing antimony is used that deposits on the catalyst surface in competition with contaminant metals, thus reducing the catalytic activity of these metals in promoting coke and gas formation. Metal passivation is especially important in fluid catalytic cracking (FCC) processes. Additives that improve FCC processes were found to increase catalyst life and improve the yield and quality of products. ... 

A number of indices relate metal activity to hydrogen and coke production. (These indices predate the use of metal passivation in the FCC process but are still reliable). The most commonly used index is 4 X Nickel + Vanadium. This indicates that nickel is four times as actiw as vanadium in producing hydrogen. Other indices [9] used are ... 

Metal passivation in general, and antimony in particular, are discussed in the following section. 

Consider reformulating the catalyst—custom formulations are available. Increasing rare-earth content can reduce the wet gas rate. Catalyst is usually selected for properties other than its ability to flow. However, if it does not flow, it is not going to work well. Catalyst physical properties should be compared with those of catalysts that have circulated well. Evaluate the economics of using metal passivation additives and other catalyst enhancing additives. 

Svare, C. W., Belton, G., and Korostofife, E., The Role of Organics in Metallic Passivation , Journal of Biomedical Materials Research, 4, 457-467 (1970)... 

Experimental installations have been established from time to time to demonstrate the possibility of using ferrous metals in anolytes " selected to minimise polarisation and to reduce metal ionisation by making the metal passive. 

Here, the use of inhibitor formulations having a less dramatic effect on TDS (such as certain tannins) may be extremely beneficial. Formulations are available that are based on tannin chemistry and contain blends that act as oxygen scavengers and metal passivators, with additional sludge dispersant and antifoam properties. 

Alkali/polymer based multifunctional formulation for hard water MU (up to 50 ppm CaCOf) in LP steam or light-industrial FT boilers. Includes a metal passivator. 

Overall, DEHA is a low toxicity product, performs extremely well as a rapid oxygen scavenger and metal passivator, and is an excellent replacement for hydrazine. In addition, it is competitively priced and consequently a very popular product. 

Metal passivators Triazole Protect yellow metals... 

To summarise, AC methods have proved most successful where the system is straightforward and can be modelled analytically. By measurement over a wide range of frequencies the constants for the reaction steps constituting the model can be established and, particularly if adsorbed species are involved, AC methods have proved very powerful indeed, with a major area of application being in the study of metal passivation, as discussed in detail elsewhere in the book. An example of this behaviour in practice is provided by the work of Conway s and Hillman s groups on chlorine evolution at platinum. Several mechanisms for this reaction have been proposed, including both Volmer and Heyrovsky types ... 

Metal oxide sensors (MOS), smart, 22 717 Metal oxide supported catalysts, 5 336-337 coke formation on, 5 267—270 Metal passivation, in industrial water treatment, 26 137 Metal peroxides, 18 410 Metal phosphates, tertiary, 18 840 Metal-phosphorus alloys, 19 59 Metal phthalocyanines, electrochromic materials, 6 572t, 576-577 Metal prefinishing, detersive systems for, 8 413t... 

Phillips Petroleum Company discovered and developed the antimony metals passivation process in the early 1970 s, and successfully applied the process at its Borger, Texas heavy oil cracker (HOC) in 1976 (2). For catalytic cracking units with... 

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