| Abstract |
A polarization experiment using diyereent Qpes of metal coupons immersed in the Upper Mahiao Condensate was conducted to elucidate the processesses that control corrosion. Results showed that low carbon steel is incapable of forming a protective layer because of the continued breah of the protective film. Austenitic stainless steel showed a very wide range of passivation zone, suggesting that it is very resistant to this type of fluid acidity. From analytical methods such as SU, EPMA, XRD and XR-Fluorescence were conducted on the corrosion samples to determine the actual chemical composition and the mophology of the corrosion products. The contrasting gect of high temperature steam and low temperature condensate to the steel facilitated hydrogen infusion which promotes blistering and su@& corrosion at the first and second stages of the turbine that breaks down the protective film into secondary corrosion products at low temperature durmg shut&wns. This l e d to the exposure of deeper steel material to acidic environment. This condition coupled with the erosive velocity of the jluid along these stages, resulted to wearing ofthe turbine parts. lhepolarization of ordinary martensitic steel (12YX'r) suggests that it is not reliably resistant to corrosion using the above fluid. Tlnss. a more appropriate material (ie. martensitic steel with higher YX'r, !%A40 and or Y&o is needed for the turbine. |