Electrochemical and initial corrosion behavior of ultrahigh strength steel by scanning Kelvin probe

Electrochemical behavior of ultrahigh strength (UHS) steel (1#) after salt spray test (SST) was studied by means of electrochemical techniques and scanning Kelvin probe, Raman spectroscopy, and scanning electron microscope. The results show that pitting occurs to the samples of 1# steel in SST with 5% NaCl. The corrosion products are mainly γ-FeOOH and oxide/hydroxide of chromium. Within 4 days, corrosion reaction is resisted by the completed corrosion products, and thereafter corrosion rate of 1# steel with corrosion products is accelerated as the SST continues, since the corrosion potential shifts to negative direction and corrosion current density becomes larger. Kelvin potentials of 1# steel after the SST are 0.3-0.4 V higher in magnitude and distributes more unevenly than that before the SST, because the oxide films grow thicker and affect the anodic reaction of corrosion process.