Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Effect of Temperature on the Pitting of Type 304 Stainless Steel in Bromide and Chloride Solutions Containing Nitrate Ion
Hitoshi YashiroEiji FujiwaraNaoaki KumagaiKatsumi Mabuchi
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2001 Volume 50 Issue 10 Pages 460-465


Pitting behavior of type 304 stainless steel has been investigated in LiBr and NaCl solutions containing nitrate ion through measurements of pitting potential (Epit) as a function of temperature, and pitting temperature (Tpit) as a function of potential. In the absence of nitrate ion, Epit in NaCl solution became less noble with temperature while Epit in LiBr solution was less sensitive to temperature. A similar relation was found between Tpit and potential. The inhibitive effect of nitrate ion against pitting was only apparent below 298K in LiBr solution and below 323K in NaCl solution. Above these temperatures, Epit was not improved significantly by the addition of nitrate. Nitrate ion inhibited pitting effectively when Epit ranged over ca. 400mV (vs. Ag/AgCl/2mol kg-1 KCl). Actually, Tpit decreased with potential up to ca. 400mV and then turned to increase in NaCl+NaNO3 solution. In LiBr+LiNO3 solution, Tpit decreased with potential up to ca. 600mV and increased slightly above it. It was estimated that LiBr solution became extremely aggressive above ca. 400mV canceling out the inhibitive action of nitrate at nobler potentials.

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