Applications of Potential-pH Diagrams

Many phenomena associated with corrosion damage to iron-based alloys in water at elevated temperatures can be rationalized on the basis of iron-water J-pH diagrams. Marine boilers on ships and hot-water heating systems for buildings are relevant practical examples. 

Marine boilers. The boilers used on commercial and military ships are essentially large reactors in which water is heated and converted to steam. While steam powering of ships engines or turbines is rapidly drawing to a close at the end of the twentieth century, steam is still required for other miscellaneous purposes. All passenger ships require 

Steel is used extensively as a construction material in pressurized boilers and ancillary piping circuits. The boiler and the attached steam/water circuits are safety-critical items on a ship. The sudden explosive release of high-pressure steam/water can have disastrous consequences. The worst boiler explosion in the Royal Navy, on board HMS Thunderer, claimed 45 lives in The subsequent inquiry 

When considering the water-side corrosion of steel in marine boilers, both the elevated-temperature and ambient-temperature cases should be considered, since the latter is important during shutdown periods. Boiler-feedwater treatment is an important element of minimizing corrosion damage. On the maiden voyage of RMS Titanic, for 

Filiform corrosion is characterized by an advancing head and a tail of corrosion products left behind in the corrosion tracks (or filaments ), as shown in Fig. 1.10. Active corrosion takes place in the head, which is filled with corrosive solution, while the tail is made up of relatively dry corrosion products and is usually considered to be inactive. 

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R. G. Robins, The Application of Potential-pH Diagrams to the Prediction of Reactions in Pressure Hydrothermal Processes, LR 80 (MST), Warren Spring Laboratory, Stevenage, London, 1968. 

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