THE ALKALINE FILM FORMING TECHNOLOGY OF RARE EARTH CONVERSION FILM ON ALUMINUM AND ITS ALLOY
铝合金稀土转化膜碱性成膜工艺T3/T7的研究

The performance of conversion films containing rare earth element on aluminum and its alloys has been studied by linear polarization technique,polarization curve measuring,and neutral salt spray test.The test results revealed that: the uniform corrosion rate in sodium chloride solution was reduced by 10 to 20 times, the films passed 504 h salt spray test without damage, after the conversion treatment both of anodic and cathodic processes of aluminum alloys corrosion were greatly inhibited, the pitting potential was obviously moved in positive direction. This revealed that resistance to pitting corrosion in chloride medium was greatly improved after rare earth conversion treatment.The result of photoelectric current spectrum in open circuit voltage indicated that rare earth conversion film basiclly was an insulator besides ion could pass through surface dissolution and exchange of positions.