Metal dusting Inhibition

The features of this failure case were similar to the previous case materials loss was observed, coke was detected and the internal wall showed a carburised zone in the metallographic cross-section. The outer surface was partially covered with the red scale and one tube had even cracked locally. Near the crack there were deposits in the tube and the microstructure of the steel indicated strong overheating. The new 9%Cr tube obviously failed due to metal dusting, coke formation inhibiting the heat transfer and locally increased temperatures. 

In principle, metal dusting could also be initiated by olefins, which are very reactive for formation of whisker carbon (Figure 5.4), but in most industrial plants (steam crackers, FCC units), olefms-containing streams contain sulphur, which will inhibit the nucleation of carbon. 

The sulphur present in the SPARG product gas (refer to Section 5.5) inhibits the nucleation of metal dusting corrosion in the outlet system, even when the operating conditions predict that carbon formation is... 

The sulphur passivation of the CO dissociation is applied for inhibition of metal dusting corrosion (refer to Section 5.2.2) on high alloy steel in the presence of S5mgas with high contents of carbon monoxide. Sulphur passivation is also used for retarding initiation of... 

Red lead, zinc chromate, calcium plumbate and zinc dust were for many years of special importance as pigments for metal primers. When dispersed in raw or lightly-treated linseed oil, the first three possess the ability to inhibit the corrosion of mild steel and will function very well on wire-brushed rusted surfaces. In other media the tolerance towards rusted surfaces decreases with decreasing quantities of available oil, but performance on clean steel will usually be maintained and often improved. 

Evidence of the relatively benign nature of aluminum dust in measured concentrations lies in the 27-year experience of administration of freshly milled metal particles to workers exposed to silica as a suggested means of inhibiting the development of silicosis. Inhalation of aluminum powder of particle size of 1.2 p, (96%), over 10- or 20-minute periods several times weekly, resulted in no adverse health effects among thousands of workers over several years. 

Platinum is a relatively rare earth metal usually found with related metals osmium and iridium. While it has a number of industrial applications, its common consumer application is in catalytic converters. This application has actually increased platinum concentrations in roadside dust. The ability of platinum and its derivatives to kill cells or inhibit cell division was discovered in 1965. Platinum-based drugs, such as cisplatin, are used to treat ovarian and testicular cancer, and cancers of the head and neck, as well as others. Unfortunately, the toxic side effects of these agents often limit their usefulness. 

The theoretical aspect of inhibition of explosions of methane-air and coal dust-air is mainly regarded from the view point of the action of alkali metals in fiame and particularly on the action of potassium ion [53 55]. 

Metal fume fever, a critical end point, was observed in workers who inhaled high levels of zinc oxide fumes or dust. The mechanism of metal fume fever has been reported to be an immune response to zinc oxide in the respiratory tract. The anemia observed in humans and animals after oral exposure to high levels of zinc could result from a zinc-induced copper deficiency. Excess levels of dietary zinc inhibit the transport of copper to the blood from either the intestinal lumen or the intestinal mucosal cell. 

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