Effect of anthanum addition on microstructure and corrosion behavior of A1-Sn-Bi anodes.doc

Effect of lanthanum addition on microstructure and corrosion behavior of A1-Sn-Bi anodes HOU Delong(侯德龙)，LI Defu(李德富)，HAN Li(韩莉)，JI Lianqin（纪莲芹)(General Research Institute for Non-Ferrous Metals ,Beijin9100088,China) Received 8 March 2010；revised 30 August 2010 Abstract：Novel AI-Sn-Bi anodes with and without lanthanum (La) were prepared．To evaluate the corrosion properties of the anodes，constant current and dynamic loop tests were carried out to determine its efficiency and corrosion rate．Optical microscopy(OM)，transmission electron microscopy(TEM)and energy spectrum analysis techniques were used to examine and analyze microstructure and corrosion behavior of the specimens．The result showed that the Al-Sn-Bi anodes with La additions revealed higher current efficiency and anticorrosion in artificial environment．Segregation phase of anodes with La additions got more homogenous than that without La additions．Its grains were fined and the amount of segregation Fe-phase was reduced． Keywords：Al-Sn-Bi sacrificial anodes；lanthanum；microstructure；comprehensive property；rare earths Cathodic protection of potable water storage containers，with magnesium sacrificial anodes ,is commonly used．The present study has focused on the development of aluminum alloys for the protection of tap water storage systems． One of the new anode materials is Al-Sn-Bi alloy．which has more advantages than magnesium alloy anodes． Aluminum anodes demonstrate reliable long term performance compared with magnesium which might be consumed before the protected steel structure has served its useful life． Aluminum also has better current／weight characteristic than magnesium． Weight can be a major consideration for some eroded environments． However, the major disadvantages of Al—Sn—Bi anodes products which are fabricated by domestic enterprises are its low current efficiency and fast corrosion velocity．The major reason is that the technology of foreign enterprise is secret for China．Therefore, it is importa