Corrosion Behavior of Sn-Bearing Steel under Wet/Dry Cyclic Environments Containing Cl⁻

Abstract

The corrosion potential and corrosion rate of steel under wet/dry transitions were investigated using the Kelvin probe/pressure difference measurement system in order to elucidate the effect of Sn on the corrosion of steel covered by a thin electrolyte film in wet/dry environments containing chloride ions (Cl ¹). The corrosion rate in the case of an electrolyte containing Cl ¹ during the drying stage was higher than that in the case of an electrolyte containing sulfate ions (SO 4 2¹). Cl ¹ accelerate the hydrolysis of Fe 3+ and lead to the acidification of the anode site in the thin electrolyte film, while also contributing to corrosion during the drying stage. The Sn-bearing steel showed a lower corrosion rate during the drying stage than that of the mild steel. This was because the Sn ions from the steel can exist stably in the acidic thin electrolyte film and inhibit the anodic reaction during the drying stage. Thus, the superior corrosion resistance of the Sn-bearing steel under atmospheric conditions is attributable to the retardation of the anodic reaction during drying by Sn ions.

Electrochemical reduction and re‐oxidation behavior of α, β, and γ‐iron oxy‐hydroxide films on electrodes

“…The corrosion rate and corrosion potential in a thin water film containing Cl − under wet to dry transition exhibited similar changes to those observed in previous studies. [10][11][12]21] The pressure in the chamber during wetting changed due to its being opened and closed to calibrate the Kelvin probe potential. Therefore, the pressure decay during the wetting stage was ignored in the present study.…”

“…The oxygen reduction (shown in Figure (a) IV) is activated, and the anodic reaction increases (Figure (a) IV). Consequently, the corrosion rate increases rapidly immediately before drying . The Cl − accumulates at the anode site in an attempt to maintain electrical neutrality (described in Figure (a) V) thus accelerating the air oxidation of Fe 2+ to Fe 3+ (described in Figure (a) VI), as well as the hydrolysis of the formed Fe 3+ as the initial reaction of β‐FeOOH.…”

“…We used a Kelvin probe/pressure difference meter system, previously used by other researchers, to measure the corrosion potential and corrosion rate . The corrosion potential and corrosion rate were measured using a Kelvin probe and pressure‐difference meter . The corrosion cycle was simulated using the same method as that used in our previous study .…”

“…[10][11][12] The corrosion potential and corrosion rate were measured using a Kelvin probe [10][11][12][13][14][15][16] and pressure-difference meter. [15][16][17][18][19][20][21] The corrosion cycle was simulated using the same method as that used in our previous study. [21] That is, the samples were covered with a thin electrolyte layer of a 0.01 M NaCl solution for the first cycle.…”

“…[15][16][17][18][19][20][21] The corrosion cycle was simulated using the same method as that used in our previous study. [21] That is, the samples were covered with a thin electrolyte layer of a 0.01 M NaCl solution for the first cycle. The thickness of the electrolyte layer was 500 µm, which was formed by placing 245 μl of the 0.01 M NaCl solution onto the specimen using a micropipette.…”