Duplex stainless steels are excellent materials for marine chemical tankers and land-based storage tanks due to their combination of good mechanical properties and corrosion resistance. The range of duplex steels from the lean duplex 1.4162, via the widely-used 1.4462 to the super duplex 1.4410 means that an appropriate grade can be selected depending on the application. The resistance to various corrosion types can therefore effectively be utilized for the storage and transportation of chemicals in marine environments. Both storage tanks and ships are exposed to air-borne chlorides, structural components on ships can be subjected to seawater splashing and seawater is often also used to clean the tanks. All these conditions give a risk of pitting and crevice corrosion.. If the proper steel grade is not used the presence of chlorides in combination with a hot surface can additionally cause stress corrosion cracking. Results from pitting corrosion tests are presented, together with data which illustrates the superior resistance of duplex stainless steels to stress corrosion cracking compared to their austenitic counterparts. There are also high demands on the uniform corrosion resistance of construction materials which are in contact with the chemical load, since different types of acids and other chemicals need to be handled. In such environments duplex stainless steels can often remain passive and thus be suitable materials. However, there are limitations and some examples, including the effect of impurities such as chlorides and the dilution of concentrated sulphuric acid, are discussed in the paper.
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