塩化物イオン混入環境におけるすきま腐食抑制技術としての非有害アニオンの効果
Effects of non-aggressive anions as a mitigation measure to crevice corrosion in a chloride containing environment
著者:
関口 智大 Tomohiro SEKIGUCHI 渡邉 豊 Yutaka WATANABE
発刊日:
公開日:
chloride ioncrevice corrosioncritical chloride ion for crevice corrosionmolybdate ionrepassivation
概要
When crevice corrosion occurs in Cl- containing solutions, Cl- concentration in the crevice increases by a few orders of magnitude due t o potential gradient. This is one of the reasons why localized corrosion takes place in a crevice. If there are non-aggressive anions ( such as MoO42-) coexist in the bulk with Cl-,it is expected that the non-aggressive anions migrate into the crevice competitively with C l- and it helps to improve the crevice environment. The purpose of this study is to investigate the effectiveness of the Na2MoO4solutio n compared to pure water to passivate growing crevice corrosion. Cl- concentration in the bulk to stop the crevice corrosion occurred o n the type 316 stainless steel when diluting bulk Cl- solution by adding pure water or Na2MoO4solution is examined. While crevice corro on did not stop at 80 ppm Cl- when diluted with pure water, The corroding crevice was passivated at 600 ppm Cl- when diluted with Na2M 4solution (1.92×10-2mol/l MoO42-). From these results, dilution with MoO42- solution is effective to improve the crevice environment.
