| Effect of carbide precipitation on pitting behavior of 304 stainless steel was studied by a potentiostatic technique. Different amounts of carbide precipitation were achieved by senstifation treatments at 800℃ for 1, 3 and 5 hours, respectively after solution treatment in vacuum atmosphere of 10＾(-6) torr Corrosion behavior of these specimens were investigated by studying polarization curves in 1.0 N H₂SO₄solution. The specimens were pitted in 1.0N H₂SO₄+0.5N HCl solution by a potentiostatic method and the morphology of the pitts was observed by a scanning electron microscope. It was found that the as-solution treated specimen showed the widest passive region and the passive region became narrower as the amounts of carbide precipitation increased. As the potential increased and amounts of carbide increased, the induction time linearly decreased and pitting rate increased. Microstrucrures of the all specimens showed slow grain boundary corrosion during the induction time region. In the pit growth region, pits were observed in the grain interior in the case of the as-solution treated specimens whereas they appeared more in the grain boundary areas in the case of the carbides precipitated specimens. As corrosion time increased, the number and size of the piles also increased. Pits appeared remarkably around twin and grain boundary regions in the specimens sensitized for 3 hrs. |
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