亞硝酸鈉對不銹鋼與鎳基超合金之腐蝕抑制性研究

The Effect of Corrosion Inhibition of Sodium Nitrite on Stainless Steels and Ni-base Superalloys

亞硝酸鈉（NaNO2）是一般鋼材在水溶液中做為除氧作用之常用腐蝕抑制劑，而不銹鋼因在鹽水中含有氯離子，易造成保護膜之局部破壞而造成孔蝕。本研究探討添加亞硝酸鈉改善三種不銹鋼（含2205 SS、304 SS及316 SS）與三種鎳基合金（含In-600、In-738及In-939）在3.5%NaCl溶液中之抗蝕性質。採用電化學循環極化法測得材料之孔蝕電位與保護電位，並配合試片浸漬測試，來評估抑制劑之抑制效率。結果顯示添加適量NaNO2能明顯改善合金之孔蝕性。

Sodium nitrite is a common corrosion inhibitor to remove dissolved oxygen in the aqueous solution for steels. Stainless steels are generally damaged by pitting corrosion because their protective film can be locally destroyed in the Cl -containing aqueous solution. This paper was to study the effect of corrosion inhibitor of NaNO2 on three kinds of stainless steels and three types of nickel based superalloys in 3.5% NaCl solution. Cyclic polarization scan was performed to evaluate the pitting potential, protection potential, and corrosion potential. The surface morphology of specimens after immersion test was observed and confirmed the pitting corrosion inhibitor effect for all specimens. The results revealed that the addition of appropriate NaNO2 can inhibit pitting corrosion.