Solid corrosion products metal dusting

Metal Dusting as a Special Form of Solid Corrosion Product.591... 

The corrosion products formed are the composition of the metal or alloy and the contaminants present in the atmosphere. For example, carbon steel does not have the ability to form its own protective coating except in a dry, clean atmosphere. Under these conditions, a thick oxide film will form that prevents further oxidation. Initiation of corrosion is the result of the presence of solid particles on the surface. This settled airborne dust promotes corrosion by absorbing SO2 and water vapor from the air. Even greater corrosive effects result when particles of hygroscopic salts, such as chlorides or sulfates, settle on the surface and form a corrosive electrolyte. 

Solid particulate materials and alkali metals in the treated gas can cause severe corrosion/erosion problems in gas turbine applications. Solid particulates in the sour gas having a mean diameter greater than 10 microns are effectively removed by the absorber and end-up in the sulfur product. This may cause discoloradon of the sulfur, and an increase in its ash content. The recommended maximum allowable particulate content is 40 milligrams of dust per actual cubic meter of sour gas feed. When an electrostatic detarrer is employed, the concentration of solid particulate is usually well below this value. 

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