Temperature dependence of crevice corrosion initiation on titanium grade-2

The temperature dependence of crevice corrosion initiation on titanium grade-2 has been investigated using a galvanic coupling technique. The film breakdown/repassivation transients indicate a temperature threshold, around 65degreesC, for the initiation of crevice corrosion. The number, size, frequency, and background current of these events increased when the temperature was increased from 65 to 80degreesC. Analysis of single transients suggests that the temperature also has an effect on the repassivation mechanism. Image analysis of corroded coupons reveals that crevice initiation and deeper penetration occur around the edge of the creviced area. Surface studies using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy show oxide film flaws accompanied by water incorporation at temperatures above the 65degreesC threshold. Under creviced conditions, the occurrence of film flaws is the key process leading to the development of acidity and the initiation of crevice corrosion. (C) 2002 The Electrochemical Society.