Pitting corrosion of passivated {beta}-tin monocrystals

Journal Article · Wed Mar 01 04:00:00 EST 1995 · Corrosion

DOI:https://doi.org/10.5006/1.3294364· OSTI ID:28025

Guo, R; Weinberg, F; Tromans, D ^[1]

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1. Univ. of British Columbia, Vancouver, British Columbia (Canada). Dept. of Metals and Materials Engineering

Anisotropic pitting behavior of tetragonal {beta}-tin (Sn) was studied on low-index surfaces of monocrystals exposed to a near-neutral aqueous solution containing 0.1 M sodium chloride (NaCl) + 0.5 M sodium nitrate (NaNO{sub 3}). The critical pitting potential (E{sub pit}) for the onset of pitting on passivated surfaces were obtained from single-cycle polarization tests conducted at a scan rate of 0.5 mV/s. Pit morphology was studied by scanning electron microscopy, supplemented by light interference microscopy. The orientations of all surfaces and the crystal directions lying in each surface were determined by X-ray techniques. It was found that the (100), (110), (011), and (001) surfaces all exhibited a similar E{sub pit} of {minus}0.288 V{sub SCE} {+-} 0.005 V{sub SCE}, whereas the (111) surface exhibited a value that was reproducibly lower (less noble) by {approximately} 20 mV. All pits displayed a crystallographic morphology, with walls and base composed of different variants of the [100], [011], and [001] planes. No variants of the [110] or [111] planes were observed inside pits. There was no correlation between the anisotropic pitting behavior and the surface atom packing density. Results were reasonably consistent with a mechanism of pit initiation determined by anodic dissolution processes at the metal-electrolyte interface at the base of existing defects (flaws) in the passive film. Such defects (or film breakdown events) alone were insufficient to cause pitting initiation.

• Sponsoring Organization: USDOE
• OSTI ID: 28025
• Journal Information: Corrosion, Journal Name: Corrosion Journal Issue: 3 Vol. 51; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CORROSION PRODUCTS
CORROSIVE EFFECTS
CRYSTAL STRUCTURE
PASSIVATION
PITTING CORROSION
SODIUM CHLORIDES
SODIUM NITRATES
TIN