Application of Electrochemical and Mechanical Impedance Measurements to Corrosion Induced Failures.
Final rept. 24 May 82-23 Jan 84,
ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
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Measurements of the electrochemical impedance for C117 C-Min steel have shown that an additional high frequency time constant occurs during straining in carbonatebicarbonate only at potentials where stress corrosion cracking SCC occurs. This time constant is related to the films which are formed in the potential region where the steel undergoes SCC. Mechanical impedance measurements allow an evaluation of the extent to which applied cyclic stress couples to electrochemical reactions. For C117 steel in phosphate pH4 and carbonatebicarbonate solutions the necessary conditions for SCC have determined from the potential dependence of the mechanical admittance the necessary conditions for SCC have been determined from the potential dependence of the mechanical admittance. The method is therefore useful for screening materials and environments for conditions which are necessary for SCC. Preliminary mechanical impedance measurements have also been carried out during corrosion fatigue of A7075-T73 in 0.5M NaCl at catholic potentials. The ac current flowing from the cracking tip allows to evaluate the phenomena which occur in the growing crack. Author
- Physical Chemistry
- Properties of Metals and Alloys