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An electrochemical approach for investigating crevice-corrosion initiation and propagation phenomena is discussed. The method varies from previous ones in that it is applicable in natural environments and requires no artificial stimulation. Quantitative measurement of electrochemical parameters provides a basis for further understanding the nature of crevice corrosion.
The test technique allows measurement of time to initiation and rate of propagation of crevices. This is achieved by electrically coupling a small test specimen (Anode) through a zero-impedance ammeter to a larger specimen (cathode). Both specimens are immersed in an electrolyte and the anode is “sandwiched” between two nonmetallic plates. This creates a crevice. The current between the cathode and the anode is monitored as a function of time.
Data are reported for Types 304 and 316 stainless steel exposed in natural seawater. Times to initiation and propagation rates as determined from current measurements are compared with visual observations of times to initiation and gravimetrically determined propagation rates.
The ability to determine a “protection” potential to prevent crevice corrosion is reviewed, and the utility of the technique in evaluating the effects of alloy and environmental variables on crevice corrosion is discussed.
crevice corrosion, localized corrosion, stainless steel, seawater, protection potential, electrochemical techniques, temperature effects
Marine Corrosion Section Manager, LaQue Center for Corrosion Technology, Inc., Wrightsville Beach, N.C.