Materials Performance Supplements


Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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inhibitor-treated pipes is magnetite oxide, Fe 2p with a binding energy of 708.2 eV (Figure 8). These observations reaffirmed that VCI pres- ence in water promotes formation of a protec- tive thin layer of black magnetite, adheres very well to steel pipe surfaces due to its magnetic properties, and provides very suitable corro- sion performance. Conclusions Corrosion behavior of CS pipe mate- rial samples in a steam/water loop with and without VCI was investigated. Electro- chemical polarization behavior showed the VCI is an anodic corrosion inhibitor and when present in the environment, expands the region of stability of a magnetite Fe 3 O 4 passive film. The passive range and film breakdown potential increased and shifted to more anodic voltage, indicating less sus- ceptibility to localized corrosion. Corrosion behavior of the steel pipe samples in boiling water showed corrosion rates for the con- trol sample to be roughly 5.3 mpy ; when 50 mg/L VCI was added, it decreased to 1.94 mpy ; and for 100 mg/L addition, the corro- sion rate dropped to 1.36 mpy. The addition of 200 mg/L reduced the corrosion rate to 0.97 mpy, while the addition of 500 mg/L resulted in a very low corrosion rate of 0.37 mpy. In boiling water, corrosion rates for the reference steel sample was ~5.3 mpy; for 100 mg/L hydrazine addition, the corrosion rate was 1.46 mpy ; and for 500 mg/L hydrazine addition, a 0.38 mpy rate was achieved. Corrosion behavior of CS pipe material samples in a steam/water loop with VCI and without inhibitor in a closed loop system of 90 psi at 118 °C showed a corrosion rate of 8.2 to 8.9 mpy, while the corrosion rate in the steam/ water closed loop with 100 mg/L VCI addition decreased to 1.09 to 1.24 mpy. In a corrod- ing system (control sample condition) when 500 mg/L VCI was injected into the closed loop system after 1,100 h, the corrosion rate dropped to 0.72 mpy. This indicates that the VCI successfully retarded corrosion reactions and managed to form stable protective oxide of magnetite on the pipe interior surfaces. This is a very impressive result; a corroding closed loop steam/water system can be recov- ered with the inhibitor treatment and its cor- rosion rate lowered to an acceptable level. FIGURE 6 Comparison of steel pipe inner surface conditions of the inhibitor treated loop and control test after 2,200 h corrosion test in hot steam/water closed loop. FIGURE 7 XPS analyses on the inner pipe surfaces after corrosion test in the hot steam loop shows more corrosion product on the control test. FIGURE 8 Comparison high-resolution XPS analyses on the inner pipe surface after corrosion test in the hot steam loop. Primary oxide seen on inner diameter (ID) surface of non-treated pipes (control) is hematite, while magnetite is predominant oxide on ID surface of VCI-treated pipes. VAPOR PHASE CORROSION INHIBITORS 14 JUNE 2018 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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