Phosphate corrosion in high pressure boilers
- Nalco Chemical Co., Naperville, IL (United States)
Phosphate treatments have been used in boilers for more than 70 years. As operating pressures increased, the frequency of corrosion-related failures in phosphate-treated boilers also increased. Many failures were attributed to ``free`` caustic generated by the nonstoichiometric precipitation of various phosphate compounds on boiler surfaces. Congruent control was devised to prevent the formation of free caustic by feeding orthophosphates so as to maintain a boiler water sodium to phosphate ratio in a range where theory surmised free caustic could not form. Unfortunately, conventional congruent control did not take into account the interaction of phosphate compounds with various deposits and corrosion products, including iron oxides on boiler tube surfaces. Corrosion continued to occur even when sodium to phosphate-pH control ranges were maintained according to theory. Phosphate corrosion is the name given to attack involving phosphate compounds having unique wastage morphologies, associated corrosion products and deposits.
- OSTI ID:
- 128686
- Report Number(s):
- CONF-950304-; TRN: IM9550%%71
- Resource Relation:
- Conference: Corrosion `95: National Association of Corrosion Engineers (NACE) international annual conference and corrosion show, Orlando, FL (United States), 26-31 Mar 1995; Other Information: PBD: 1995; Related Information: Is Part Of Corrosion/95 conference papers; PB: 5788 p.
- Country of Publication:
- United States
- Language:
- English
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