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A number of alloys, including stainless steels, aluminum, and nickel-based alloys, are used in seawater for various applications. The localized corrosion of these materials is affected, among other factors, by temperature, microbial activity, chlorination, and fl ow rate. A predictive model, based on the calculation of repassivation and corrosion potentials, is presented and compared to fi eld experiences of these alloys in seawater systems. An empirical model is used for calculating the repassivation potential of these alloys as a function of seawater composition. A mechanistic model is used for calculating the corrosion potential as a function of oxygen and chlorine concentrations. The parameters for the corrosion potential are derived from tests in fl owing natural seawater or synthetic seawater. The model calculations agree with the relative ranking of these alloys in seawater. Limitations of the current model and improvements are suggested.

The proposed waste packages for the disposal of high-level radioactive waste at the potential repository at Yucca Mountain, Nevada, consist of an outer container and inner container. The outer container is made of alloy 22, a corrosion-resistant Ni-Cr-Mo-W alloy, while the inner container is made of type 316 nuclear-grade stainless steel. Fabrication processes such as welding and postweld heat treatments can induce changes to the microstructure of alloy 22. Such microstructural changes can reduce ductility and impact strength and promote localized corrosion. Environmental conditions within the emplacement drifts, such as composition of solutions contacting the waste packages, can also affect localized corrosion susceptibility. In this study, the effects of fabrication processes on impact strength, fracture toughness, and crevice-corrosion resistance of alloy 22 were investigated.

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