Effect of liquid droplet impingement on electrochemical passivation behavior of 321 stainless steel in 0.5 wt% NaCl solution

Liquid droplet impingement (LDI) treatment changes the roughness and introduces residual compressive stress on 321 stainless steel (SS). Compared to untreated 321 SS, 1 h of LDI treatment with 100, 150 and 175 m/s gradually increases the pitting potential of 321 SS, while 1 h of LDI treatment with 200 m/s decreased the pitting potential of 321 SS. The passive films grown on the 321 SS after LDI treatment with 100, 150 and 175 m/s show a decreased receptor density, an increased Cr content and an increased thickness, whereas a dense passive film with good corrosion resistance cannot be formed on the 321 SS after LDI treatment with 200 m/s. The effect of the change in surface state due to LDI treatment on the electrochemical passivation behavior is explained in detail.