| Popis: |
The role of passivation kinetics, film ductility, and tarnish film formation in stress corrosion cracking were each examined in the following studies: (1) Ellipsometry measurements of film growth kinetics on iron have been made for two anions whose solution cause stress cracking of steel (nitrate and hydroxide) and two that do not (chloride and nitrite). (2) A technique has been developed to measure film ductility directly. This technique couples an ellipsometer with a tensile machine. Thin films on Ta show a ductility of 3-4% in the presence and absence of F(-), an ion thought to decrease ductility. (3) Pure copper forms tarnish films in cupric acetate and sulfate solutions. It is susceptible to stress corrosion cracking in cupric acetate solution. In the absence of stress, oxide forms all over the copper surface, while stress concentrates oxide formation at the grain boundaries. These experiments point ot a brittle-film rupture mechanism of stress cracking. |
