Industrial corrosion types

With respect to corrosion, the conventional classification of climates in marine, inland, industrial, etc. types is not sufficient. It should now be specified with respect to the actual chemical components in the atmosphere, as well as humidity and other factors. Recent research in this field has led to much more precise methods for estimating corrosion rates in polluted atmospheres (38). Economically, perhaps even more important problems are caused by the increased corrosion of water supply pipelines. Not only copper is dissolved, but also cadmium from soldered joints, and larger steel and cement pipelines may also be affected. 

In the typical sweet conditions of an oil and gas industry, the same steel would be subject to generalized corrosion of mesa corrosion type for temperatures below SO C, to forms of corrosion more or less localized between 80°C and 120°C, and to passivation conditions and negligible corrosion rates at temperatures above 120°C. 

CC. This also common grade contains 16 to 18% chromium and 11 to 14% nickel (316 SS). It also has molybdenum added to the nickel and chromium of the 304 material. The molybdenum is added to control pitting corrosion. Type 316 is used in chemical processing the pulp and paper industry for food and beverage processing and dispensing and in more corrosive environments. The molybdenum content must be a minimum of 2%. 

Results were obtained for chemicals with phosphono and/or carboxyl groups various types were used in order to replace very effective but toxic inhibitors, and to decrease the phosphorus content in the inhibitor. Positive correlation was found between the number of substituents with negative charge, especially with phosphono groups. As these compounds are derivatives of natural amino acids, their catabolism results in nontoxic chemicals, and the ratio of the phosphorus is lower than in the chemicals used as industrial corrosion inhibitors. Electrode impedance measurements pointed to the importance of time in the formation of a protective layer on the metal surface. 

The actual importance of each corrosion type will also differ between systems, environments, and other operational variables. However, there are surprising similarities in the corrosion failure distributions within the same industries as can be seen by comparing Figs. 6.2(a) and b). Both corrosion failure distribution charts represent... 

Corrosion types can also be categorized based on what type of environment they take place. Accordingly, major corrosion types are atmospheric corrosion, corrosion in fresh water, corrosion in seawater, corrosion in soils, corrosion in concrete and corrosion in the petroleum industry. 

In addition to the reduction in performance, flow maldistribution may result in increased corrosion, erosion, wear, fouling, fatigue, and material failure, particularly for Hquid flows. This problem is even more pronounced for multiphase or phase change flows as compared to single-phase flows. Flow distribution problems exist for almost all types of exchangers and can have a significant impact on energy, environment, material, and cost in most industries. 

Heat/Solvent Recovery. The primary appHcation of heat pipes in the chemical industry is for combustion air preheat on various types of process furnaces which simultaneously increases furnace efficiency and throughput and conserves fuel. Advantages include modular design, isothermal tube temperature eliminating cold corner corrosion, high thermal effectiveness, high reHabiHty and options for removable tubes, alternative materials and arrangements, and replacement or add-on sections for increased performance (see Furnaces, fuel-FIREd). 

Al—Mg—Si types have excehent corrosion resistance in most weathering exposures including industrial and seacoast atmospheres. Ahoys based on additions... 

Refractories are materials that resist the action of hot environments by containing heat energy and hot or molten materials (1). There is no weU-estabhshed line of demarcation between those materials that are and those that are not refractory. The abiUty to withstand temperatures above 1100°C without softening has, however, been cited as a practical requirement of industrial refractory materials (see Ceramics). The type of refractories used in any particular apphcation depends on the critical requirements of the process. For example, processes that demand resistance to gaseous orHquid corrosion require low permeabihty, high physical strength, and abrasion resistance. Conditions that demand low thermal conductivity may require entirely different refractories. Combinations of several refractories are generally employed. 

Other martensitic grades are Types 501 and 502. The former has >0.10% and the latter <0.10% carbon. Both contain 4—6% chromium. These grades are also air-hardened, but do not have the corrosion resistance of the 12% chromium grades. Types 501 and 502 have wide appHcation in the petroleum industry for hot lines, bubble towers, valves, and plates. 

Water Treatment. Sodium sulfite is an agent in the reduction of chlorine or oxygen in water. Dissolved oxygen in boiler water tends to enhance pitting and other types of corrosion. In boilers operated at below 4.82 MPa (700 psi), a residual concentration of 30 ppm of sodium sulfite is generally effective. Catalytic amounts of cobalt are often added to accelerate the reaction of oxygen with sulfite (321,322) (see Water, industrial water treatment). 

Acid Coolers. Cast Hon trombone coolers, once the industry standard (101), are considered obsolete. In 1970, anodically passivated stainless steel sheU and tube acid coolers became commercially available. Because these proved to have significant maintenance savings and other advantages, this type of cooler became widely used. Anodic passivation uses an impressed voltage from an external electrical power source to reduce metal corrosion. 

Corrosion Resistance. Titanium is immune to corrosion in all naturally occurring environments. It does not corrode in air, even if polluted or moist with ocean spray. It does not corrode in soil and even the deep salt-mine-type environments where nuclear waste might be buried. It does not corrode in any naturally occurring water and most industrial wastewater streams. For these reasons, titanium has been termed the metal for the earth, and 20—30% of consumption is used in corrosion-resistance appHcations (see Corrosion and corrosion inhibitors). 

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