Suppression of Corrosion Growth of Stainless Steel by Ultrasound

Effect of ultrasound on initiation, growth and repassivation behaviours of pitting corrosion of SUS 304 steel in NaCl aqueous solution

“…This indicates that US suppressed the initiation of pitting corrosion, similar to that observed during the growth stage of pitting corrosion. [14][15][16][17][18][19] This result can be more clearly seen in the measurement of accumulated electric charge during the PH, with the value of 2.8 kC m 22 in the absence of US at i 0 ¼ 0.1 A m 22 being reduced to 1.4 kC m 22 . The accumulated electric charge is an indicator of the dissolution of metal ions into solution during this period.…”

“…8 In addition, the growth of both the pitting corrosion and the crevice corrosion of stainless steel could be suppressed by applying ultrasound (US) in NaCl aqueous solution. [14][15][16][17][18][19] These findings were likely due to the removal of corrosion products on or within the pits and crevices by the microprobe or ultrasonic cavitation, which can diminish the enrichment of Cl 2 and H þ ions in the growing pits or crevices. In the case of pitting corrosion, US was found to remove the metallic covers.…”

“…In the case of pitting corrosion, US was found to remove the metallic covers. 6,7,19 The ability of US to suppress the growth rate of corrosion pits of SUS 304 stainless steel increased as the cavitation power at a specific frequency increased; this cavitation power was determined by either the output power to the US vibrator or the distance from the vibrator to the steel surface. 18 However, the effect was diminished when the cavitation power was over a specific value.…”

“…18 However, the effect was diminished when the cavitation power was over a specific value. 18,19 Although the ability of US to suppress the growth of pitting corrosion of stainless steel is likely associated with the repassivation of the pits, this has not been directly investigated. Furthermore, the effect of US on the initiation behaviour of pitting corrosion has not been assessed.…”

“…Previous studies have shown maximum suppression at these US conditions. 18,19 Polarisation was started from E SCE ¼ 2600 mV at the cathode side and then swept to the anode side at a constant increase in potential of 0.33 mV s 21 under control of the potentiostat.…”