2009 Volume 58 Issue 11 Pages 378-385
Potentiostatic tests of stainless steel specimens with crevice between metal and glass were carried out in 460 ppm Cl− solution at temperatures of 298 K, 323 K and 353 K in order to clarify effects of potential and temperature on incubation time, tINCU, for crevice corrosion. The test surfaces were polished just before the tests.
The tINCU increased with the decrease in potential. The charge density, QINCU, which was required for initiation of crevice corrosion, was independent of potential in constant temperature conditions, and it decreased with the increase in temperature. It is considered that hydrolysis reaction rate of dissolved metal ions increases with temperature, and therefore pH of anolyte within crevice can decreases below depassivation pH with few amounts of dissolved metal ions or increase of chemical dissolution of passive film , and the both.
It is because potential dependence of tINCU is derived from increase of iINCU, average dissolution current density of metal with noble potential. For all kinds of stainless steels tested, tINCU and QINCU decreased with the increase in temperature, and iINCU, on the other hand, increased with temperature. From Arrhenius plotting of these parameters, activation energies of tINCU, iINCU and QINCU for various kinds of stainless steels were obtained, and reactions during crevice corrosion occurrence were presumed.