Abstract
In the use of stainless steels at seawater environment, pitting or crevice corrosion of stainless steels become a problem. It was reported that the potential of stainless steel in natural seawater environment rises more noble than in artificial seawater. On the other hand, it is well known that alloying chromium, molybdenum or nitrogen are effective in order to improve pitting and crevice corrosion resistance of stainless steel. The purpose of this study is to obtain a guideline for creation of high nitrogen-bearing stainless steel with excellent localized corrosion resistance. For that reason, it was investigated the effect of alloy elements on localized corrosion resistance for nitrogen bearing stainless steels. 17%Cr-14%Ni-2%Mo-0.2%N based stainless steels were used as test samples. Chromium, molybdenum and nitrogen contents were changed. Pitting potential in artificial seawater was measured. And crevice corrosion loss in simulated environment for seawater was estimated. As a result, chromium, molybdenum and nitrogen improve pitting and crevice corrosion resistance. It was shown that there was a synergistic effect between molybdenum and nitrogen. Crevice corrosion resistance of nitrogen bearing stainless steels was electrochemically investigated. It was cleared that crevice corrosion potential measured in potentiostatic after potentiodynamic method showed higher potential than in potentiostatic method. This behavior is probably caused by difference of surface statement. The guideline for creation of high nitrogenbearing stainless steel used in seawater environment was obtained.
