Investigation On Corrosion And Protection Of Magnetic Refrigerating Material Gadolinium

Room temperature magnetic refrigeration has attracted more and more attentions due to its advantages in energy saving and environmental protection. Of several key problems in the technology, magnetic refrigerating material has played an important role. However gadolinium, a good magnetic regenerating material, is easy to erode in refrigerating liquid containing system, so the cooling efficiency and cycle life of magnetic refrigeration are harmed obviously. In this thesis, it is investigated that the corrosive behaviors, anticorrosive technologies and anticorrosive mechanism of gadolinium in refrigerating liquid. The research results are as follows: 1) The single Na2MoO4 with addition of more than 300mg/L has an anticorrosive effect but not enough ideal, while a compound salt of Na2MoO4, Na2SiO3 and Zn2SO4 has an distinctly anticorrosive effect with a nearly zero corrosive rate;(2)The main corrosion of Gd in magnetic refrigerator is due to electrochemistry and gap effect, but it could be solved by increasing the addition amount of anticorrosive compounds and coating an insulating film on stainless steel; (3)The corrosive compounds on the surface of Gd, found by XPS techniques, are Gd2O3 in pure water, MoO2 in single Na2MoO4 containing water, and MoO2 as well as SiO42- in the compound salts containing water; ( 4)Na2MoO4, as an anode inhibitor, can retain the corrosion of anode, while Na2SiO3 remedies the disfigurement of Na2MoO4 film due to the formation of the SiO42- deposition film, that the addition of both inhibitors play an very impactful anticorrosive effect.