Boiler corrosion

Steam boilers are constructed according to various designs, but they consist essentially of a low-carbon steel or low-aUoy steel container for water that is heated by hot gases. The steam may afterward pass to a superheater of higher-alloy steel at higher temperature than the boiler itself. For maximum heat 

The history and causes of corrosion in power-station boilers have been reviewed by Mann [11] case histories of corrosion and its prevention in industrial boilers have been presented by Frey [12]. 

Some boilers are equipped with an embrittlement detector by means of which the chemical treatment of a water can be evaluated continuously in terms of its potential ability to induce stress-corrosion cracking (Fig. 18.3) [13]. A specimen of plastically deformed boiler steel is stressed by setting a screw adjustment of this screw regulates a slight leak of hot boiler water in the region where the specimen is subject to maximum tensile stress and where boiler water evaporates. A boiler water is considered to have no embrittling tendency if specimens do not crack within successive 30-, 60-, and 90-day tests. Observation of the detector is 

Corrosion of boiler and superheater tubes is sometimes a problem on the hot combustion gas side, especially if vanadium-containing oils are used as fuel. This matter is discussed in Sections 11.8 and 11.9. On the steam side, since modern boiler practice ensures removal of dissolved oxygen from the feedwater, a reaction occurs between H2O and Fe, resulting in a protective film of magnetite (Fe304) as follows  

The mechanism of this reaction, so far as it is understood, indicates that Fes04 is formed only below about 570°C (1060°F) and that above this temperature, FeO forms instead. The latter then decomposes on cooling to a mixture of magnetite and iron in accord with 

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The dibydrochloride salt is used as a photographic developer. It also is employed as an intermediate in the manufacture of fur dyes, in hair dyeing, as a reagent in testing for ammonia and formaldehyde, and as an oxygen scavenger in water to prevent boiler corrosion (173). 

Figure 5 shows the phosphate—pH relationship recommended to control boiler corrosion. Different forms of phosphate consume or add caustic as the phosphate shifts to the proper form. For example, addition of monosodium phosphate consumes caustic as it reacts with caustic to form disodium phosphate in the boiler water according to the following reaction ... 

To protect steam boilers and their tubes from corrosion, E. Cumberland used cathodic impressed current in America in 1905. Figure 1-10 has been taken from the corresponding German patent [35]. In 1924 several locomotives of the Chicago Railroad Company were provided with cathodic protection to prevent boiler corrosion. Where previously the heating tubes of steam boilers had to be renewed every 9 months, the costs fell sharply after the introduction of the electrolytic... 

Ulanovskii, I. B., Conditions for Cathodic Protection of Stainless Steels in Crevices , Zashchita Metal, 1, 643 (1965) C.A., 64, 10751 Holmes, D. R. and Mann, G. M. W., A Critical Survey of Possible Factors Contributing to Internal Boiler Corrosion , Corrosion, 21, 370 (1965)... 

The prime reaction in boiler corrosion is the formation of magnetite and hydrogen from iron and water ... 

This last design (chloride anion exchange) is very often specified when some form of dealkalization plant is under consideration. Selection usually is made on the grounds of operator safety and reduced risk of boiler corrosion. Although it may have the attraction of not creating any potential for acid handling or acid introduction into the FW line or not requiring a deaerator, these are mere diversions. 

Steam/CR system corrosion debris pickup, tranport, and re-deposition. Wide ranging FW line blockages and impingement/erosion Enhances risk of pre-boiler corrosion... 

The transport of pre-boiler corrosion debris to the boiler section includes the oxides of iron, copper, nickel, zinc, and chromium and results from the corrosion of pre-heaters and condensers, and the like. Specifically, equipment components variously fabricated from admiralty brass, aluminum brass, cupronickels, and stainless steels are most affected. 

Ammonium carbamate NH2Fe2(OH)4(CO3)2-H20 Hydrated basic ferric The transport of pre-boiler corrosion debris to the boiler section will includes these minerals. Also the oxides of Fe, Cu, Ni, Zn, and Cr as... 

Oxygen-influenced boiler corrosion problems (Cont.)... 

Westwood, H.J., Lee, W.K., Corrosion-Fatigue Cracking in Fossil-Fueled Boilers, Corrosion Cracking, Proc. in the International Conf. on Fatigue, Corrosion Cracking, Fracture Mechanics and Failure Analysis, ASM, Salt Lake City, UT, pp. 23-34, 1986. 

Two Glasgow women chemists were employed directly by the Admiralty as analytical chemists. Ada Hitchens (see Chap. 6) was assigned to work in the Admiralty Steel Analysis Laboratories, while Ruth Pirret (see Chap. 7) became a wartime researcher on marine engine boiler corrosion for the British Admiralty.42... 

Contaminants AS WELL AS feedwater. Water treatment fault. Fouling of boiler. Corrosive steam. 

Utilization. For example, Be and the chalcophile elements, As, Cd, Hg, Pb, and Se, which are released during coal combustion or leached from coal waste products, can present significant environmental hazards halogens such as Cl and F can cause severe boiler corrosion and volatilized Ni, Ti, or V can cause corrosion and pitting of metal surfaces. On the positive side, some trace elements (e.g., Ge, Zn, U, and Au) may eventually prove to be economic by-products of coal utilization, while other elements (e.g., B) may be useful in helping to understand depositional environments and to correlate coal seams (7.8). 

Ameenex. [Chemron] Tall oil amido-amine industrial surfactant corrosion inhibitor, wetting agent emulsifier, antistripping agent for mineral flotation, asphalts, boiler corrosion control. 

Cor-Trol. [Betz Industrial] Boiler corrosion inhibitor. 

Considerable progress has been made in elucidating the mechanisms and causes of boiler corrosion. Advances in this area have been assisted by the development... 

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