The
pitting growth for 304
stainless steel in 0.5mol/L NaCl and its
inhibition by
piperidine(PD) were investigated by means of atomic absorption spectrometry(AAS) and pitting current-time curve measurements under potentiostatic condition. According to AAS data, Fe, Ni and Mn in
pits dissolved into ions in form of divalence, and Cr in form of trivalence both in the presence and absence of PD. The ratios by which each component element of 304 stainless steel dissolved played a very important role in pitting self-propagation process. The self-propagation effect decreased with downward shift of the dissolution ratio of Cr because the decrease in pH in pits could be ascribed mainly to the hydrolysis of Cr3+. PD inhibited 304 stainless steel from pitting growth by decreasing the total amount of dissolved ions and the dissolution ratio of Cr. On the basis of pitting growth
kinetics, the influence of PD on the type of pit configuration was analysed. The results showed that the addition of PD turned the pits into those with slower development rate. The possible inhibition mechanism on pitting development was also discussed.
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