Catastrophic corrosion, high-temperature

One person in a unit retrieved a two-year-old shutdown procedure from his locker and tried to use it. The old procedure was significantly different from the updated procedure. If the old procedure were followed exactly, there would be more risk. If the two procedures were intermingled, there would be high temperature and catastrophic corrosion. The unit management team tore up the bootleg procedure and added the updated shutdown procedure to the controlled document system used for ISO 9002 (ISO 9000, 1994). In this document system, only the current procedure is available. Alternate systems may use an expiration date or require periodic reconfirmation. 

R. F. Hochman, Catastrophic deterioration of metals at high temperature in carbonaceous environments, Proc. Fourth Int. Congress on Meta Corrosion, NACE, 258-263 (1972). 

A common problem in boilers is the occurrence of calcium oxide build-up on the heating elements. This is not a corrosion problem in itself, because it is caused by a chemical reaction in the water at high temperatures. However, a scale deposit present on a metal surface may cause corrosion under the deposit. This type of underdeposit corrosion can be aggravated when corrosive species such as sulfides and/or chlorides are present in the water. While scale deposits reduce the thermal conductivity of the steel, and thereby increase energy costs, corrosion of the heating element can lead to a catastrophic tubing failure, which requires costly repairs. 

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