Failure analysis of bank front boiler tubes

Waterside corrosion problems can seriously affect reliability of boiler systems. Two significant of waterside corrosion mechanisms are caustic corrosion and phosphate corrosion. Two critical factors contribute to these failures. The first is availability of NaOH or of alkaline-producing salts. The second contributing factor is the mechanism of concentration. In this paper a case study on bank front tubes are presented. Different tests and examinations including visual examination, optical microscope, SEM, and XRD revealed the root causes of this boiler-tube failure were caustic and phosphate corrosion.