Manganese dioxide-coated condensers - treated with nitric acid before after-forming to prevent deterioration in impedance

摘要

In the prodn of an electrical condenser by forming a dielectric oxide coating on an electrode of valve metal, producing a semiconducting MnO2 coating on this and forming again, the MnO2 coating is treated with HNO3 before forming again. This eliminates or considerably reduces the deterioration in electrical impedance during operation or artificial ageing. Treatment is carried out with dilute HNO3 (1:1 mixt. by vol of conc. HNO3 and H2O) near its b.pt. for ca 10 min. After treatment the MnO2 coating is dried at 200 degrees C. When several MnO2 layers are produced, treatment is carried out after the prodn. of about every fifth layer.