Pitting corrosion of passivated zinc monocrystals

Journal Article · Mon May 01 04:00:00 EDT 1995 · Corrosion

DOI:https://doi.org/10.5006/1.3293600· OSTI ID:46076

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

The pitting and polarization characteristics of low-index surfaces of zinc monocrystals were studied in weakly alkaline (pH 9.2) solutions containing 0.1 M sodium chloride, using single-cycle potentiodynamic polarization tests and a scan rate of 0.5 mV/s. Tests were conducted in the presence and absence of a bicarbonate/carbonate buffer. Electrode surface orientations and crystallographic directions lying in these surfaces were determined using X-ray techniques. The surfaces were close to the (0001), (10{bar 1}0), and (11{bar 2}0) planes. Pit morphology was studied by scanning electron microscopy. Passivity was observed only in the buffered solution, and pitting of the passivated surface occurred near {minus}0.85 V{sub SCE}. The (0001) basal plane appeared to have a slightly better pitting resistance and a lower passive current density than the other orientations. Basal plane surfaces prepared by cleavage exhibited superior resistance to anodic dissolution in the unbuffered solution. Crystallographic pitting geometries observed on passivated crystals were attributed to the enhanced resistance of the (0001) plane to active dissolution. Events leading to pit initiation were reviewed in terms of localized changes in solution chemistry that resulted in a decreased pH and formation of soluble zinc chloride ion complexes (ZnCl{sub x}{sup [2{minus}x]+}).

• OSTI ID: 46076
• Journal Information: Corrosion, Journal Name: Corrosion Journal Issue: 5 Vol. 51; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CAVITIES
CORROSIVE EFFECTS
CRYSTAL STRUCTURE
PASSIVATION
PITTING CORROSION
SHAPE
SODIUM CHLORIDES
ZINC
ZINC CHLORIDES