Effects of phosphate environments on turbine materials. Final report

Technical Report · Wed Aug 01 04:00:00 EDT 1984

OSTI ID:6459211

Chen, M C; Shalvoy, R S; Gould, G C

An extensive survey of turbine damage has demonstrated much less corrosion related damage with turbines supplied by drum boilers than those supplied by once through steam generators. Since sodium phosphate salts are used extensively in drum boiler water treatment it was hypothesized that the phosphates may inhibit corrosion or stress corrosion cracking caused by common corrosive turbine deposits. In order to test this hypothesis, general corrosion rate, pitting corrosion resistance, and stress corrosion susceptibility of several common turbine materials were determined in aqueous solutions of chloride, hydroxide and phosphate as well as mixtures of these chemicals. Fast and slow potentiodynamic scans were made, pitting potentials measured and extensive slow strain rate testing was carried out on turbine wheel steel, rotor steel and bucket steel. In addition, some deadweight loaded stress corrosion tests were carried out. Sodium phosphates strongly inhibit the pitting corrosion induced by sodium chloride but show only limited inhibition effect on stress corrosion cracking and the general corrosion of the wheel and rotor steels in hot caustic solutions. At low pH, phosphate solutions induce stress corrosion cracking and cause severe general corrosion in the wheel and rotor steels. Based on the results obtained in this study, the hypothesis is probably incorrect.

• Research Organization: General Electric Co., Schenectady, NY (USA). Turbine Technology Lab.
• OSTI ID: 6459211
• Report Number(s): EPRI-CS-3541; ON: TI84920532
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
42 ENGINEERING
420500 -- Engineering-- Materials Testing
CHEMICAL REACTIONS
CHEMISTRY
CORROSION
CORROSION FATIGUE
ENVIRONMENT
FAILURES
FATIGUE
MACHINERY
MECHANICAL PROPERTIES
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PITTING CORROSION
STEAM TURBINES
STRESS CORROSION
TURBINES
TURBOMACHINERY
WATER CHEMISTRY