The effects of Sn content and simultaneous addition of selected alloying elements, such as Sn and Cu, each in slight amount, on the corrosion behavior of austenitic stainless steel of Type 304 have been investigated by using mainly electrochemical means in sulfuric acid solution. The main results obtained are summarized as follows: Sn exists in the matrix in solid solution, but is absent in nonmetallic inclusions.The corrosion rate in boiling 5wt% H2SO4 solution was remarkably reduced by addition of less than 0.5wt% Sn to the steel, and was further reduced by simultaneous addition of Sn and Cu. The reason why Sn improved the corrosion resistance of the steel was that the cathodic reaction and the anodic dissolution reaction in the active region were retarded by the presence of the surface film formed as a result of deposition of Sn in the form of oxides, SnO and/or SnO2. Therefore, until the film is formed on the steel surface, addition of Sn to the steel results in degraded corrosion resistance because of preferential dissolution of that element. Simultaneous addition of Sn and Cu makes the anodic reaction to retardation, and the resistance to dissolution in activated region to increase.
The effects of alloying elements, Sn and Cu, on the corrosion behavior of austenitic stainless steel of type 304 have been investigated by electrochemical techniques aqueous solutions of organic acids as food additive. Corrosiveness of lactic acid to type SUS 304 steel was stronger than that of other organic acids. The corrosion rate of the steel in boiling aqueous solution of lactic acid was reduced by addition of less than 0.5% Sn to the steel, and was further reduced by simultaneous addition of Sn and Cu. The reason why Sn or Cu improved the corrosion resistrance of the steel was based on that the cathodic reaction and the anodic dissolution reaction in the active region were retarded by the surface film formed as a result of deposition of Sn or Cu. Therefore, until the film is formed on the steel surface, addition of Sn or simultaneous addition of Sn and Cu to the steel results in degraded corrosion resistance because of preferntial dissolution of the elements.
Aim: The aim of this study is to determine public health nurses' support process for specified expectant mothers (Tokutei-ninpu), as pregnant, postpartum, and child-rearing women with special needs.Methods: Participants were 11 public health nurses with more than five years' experience with maternal and child health,and experience concerned with the same specified expectant mothers more than two times during the pregnancy and delivery period. Support process for pregnant women with special needs were examined through semi-structured interviews. The data were analyzed using the grounded theory approach.Results: We found that public health nurses' support process for pregnant women with special needs focused on [identifying maternal attachment capacities]. This process was explained by five categories: building relationships between pregnant women and public health nurses, finding locations to depend on neighborhood people (pregnant women's indulgent dependency or amae), identifying capacities for pregnant life, providing continual support for pregnancy, and providing a support net for pregnancy and infant security.Conclusions: The social vulnerability of pregnant women with special needs shifted to independence through the power of neighborhood support; public health nurses assessed the internal psychological function of pregnant and enlisted community resources for infant security.
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