Corrosion Resistance of Stainless Steels Used for Ships

Abstract

The corrosion resistance of several stainless steels used for ships was considered from the viewpoints of pitting corrosion, crevice corrosion, intergranular corrosion and corrosion due to several cargoes, and the following results were obtained.(1) Corrosion resistance, especially against crevice corrosion of Type 316 L, 316 LN, 317 L and 317 LN stainless steels must be improved considerably in order to use these stainless steels in seawater without any anxiety, though addition of more molybdenum and nitrogen improves the corrosion resistance of these stainless steels.(2) More severe quality control is required for the production of stainless clad steel plates than that of solid stainless steel plates, since the former has disadvantage in sensitization and precipitation of σ phase.(3) Corrosion resistance of stainless steels against cargoes in chemical tankers is affected by environmental factor of impurities contained in cargoes and by metallurgical factors of molybdenum content and sensitization.(4) It is necessary in chemical tankers to make the cleaning time of tanks by seawater as short as possible and to rinse the tanks with fresh water, in order to avoid the very harmful corrosion of tanks due to the seawater.