Effect of Si Content on the Pitting Corrosion Behavior of Ferritic Heat‐Resistant Stainless Steel in NaCl–KCl Solution

The effect of Si content on the pitting behavior of X10CrAlSi18 ferritic heat‐resistant stainless steel (FHSS) in a 1.0% (mass fraction) NaCl–KCl solution (with a NaCl to KCl ratio of 1:1) is investigated using electrochemical techniques. The conclusion is that the pitting corrosion resistance of FHSS initially increases and then deteriorates as the Si content rises, and the 0.3Si FHSS shows the best pitting corrosion resistance. Specifically, increasing Si content leads to the formation of a dense SiO 2 protective film at the early stage of pitting, providing certain protection to the substrate. However, higher Si content also causes an increase in both the quantity and size of Cr‐rich M 23 C 6 carbides within the matrix, resulting in the formation of Cr‐depleted regions around them. Moreover, the continuous development of a weak passive film in the Cr‐depleted region raises the possibility of pitting nucleation and propagation, thus reducing the pitting resistance of the FHSS.