Characterization of Boundwater in Passive Film of Type 304 Stainless Steel Formed in H₂SO₄ and NaCl Solutions

Abstract

Boundwater in the passive film on Type 304 stainless steel was characterized using a thermal desorption gas analyzer. The passive film was produced electrochemically in a H2SO4 solution and was modified electrochemically in an NaCl solution. In case of producing the passive film in the H2SO4 solution, total amount of the boundwater was relatively large in the initial stage, and then decreased as the passivation time elapsed. In addition, it was found that the boundwater was classified into three types of binding states in the passive film. When the passive film was modified in the NaCl solution, the boundwater, especially of the second type, increased.

Pitting Corrosion of Titanium Depending on the Properties of the Passive Film

“…The finding suggests that the pitting corrosion is also suppressed by enlargement of the amount of water desorbed from the passive film, consistent with the previous report. 12 The correlation between the total amount of desorbed water and the film thickness was summarized in Fig. 14.…”

“…The TDS test was carried out to determine the amount of water desorbed from the film. [12][13][14][15] Schematic illustration of a TDS apparatus (TDS-200-L STANDAM, ULVAC) is shown in Fig. 1.…”

“…The research demonstrated that the amount of the water decreased and the pitting corrosion resistance enhanced as the passivation time increased. 12,13 Our group also tried to grasp the correlation between pitting resistance of Al and the amount of the water in the porous anodic oxide film on it. The film was electrochemically formed in H 2 SO 4 solution, and electrochemically modified in NaCl solution.…”

Using Atomic Force Microscopy to Measure Thickness of Passive Film on Stainless Steel Immersed in Aqueous Solution

“…In aqueous solution (a), passive film forms with the hydration of metal atoms, generally following dehydration involving deprotonation 27,38,39 . More water molecules can be contained at potentials below 0.4 V (vs. SCE) in 0.5 M H 2 SO 4 38 , when a larger number of hydroxy groups and water molecules would be present in the film 38,40,41 . The hydroxy groups bond to metallic ions, while the water molecules exist mainly as little water of crystallization and adsorbed water in the film 27,38 .…”

“…The hydroxy groups bond to metallic ions, while the water molecules exist mainly as little water of crystallization and adsorbed water in the film 27,38 . The water molecules in passive film are thought to play an important role in stabilizing and repairing it 27,38,39,41 . Furthermore, PMRS analysis in situ showed much Cr 3+ was contained in the outmost 0.5 nm layer on Fe-19Cr alloys in solutions at pH 2.0 and 6.0 16 , without giving any information about hydroxy groups.…”