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Localized corrosion of binary Mg-Nd alloys in chloride-containing electrolyte using a scanning vibrating electrode technique

Version 2 2024-06-02, 23:52
Version 1 2023-11-03, 04:46
journal contribution
posted on 2024-06-02, 23:52 authored by G Williams, K Gusieva, Nick BirbilisNick Birbilis
The influence of neodymium (Nd) alloying additions in the 0.47 wt% to 3.53 wt% range on the localized corrosion behavior of Mg, when freely corroding in aqueous sodium chloride (NaCl) electrolyte, is investigated using an in situ scanning vibrating electrode technique (SVET). For all samples, the point of surface breakdown is an intense focal anode that expands radially with respect to time, revealing a cathodically activated interior, which is galvanically coupled with the local anode at the perimeter. However, for Nd compositions of ≤0.74%, radial expansion ceases within ca. 2 h of initiation, whereupon dark filiform-like corrosion features are observed, which traverse over the exposed Mg surface. For Nd additions of ≥1.25%, the radial expansion continues with time up to a point where the entire intact surface becomes consumed. The intensity of the local anode ring of circular corroded regions is seen to increase as more cathodically activated corroded surface becomes exposed. Mean current density values measured within these corroded areas increase progressively with Nd content, leading to a progressive rise in localized corrosion rates. The cathodic activation of corroded regions is proposed to derive from an enrichment of noble, Nd-rich intermetallic grains caused as the alpha-Mg phase becomes attacked at local anode sites.

History

Journal

Corrosion

Volume

68

Pagination

489-498

ISSN

0010-9312

eISSN

1938-159X

Language

English

Publication classification

C1.1 Refereed article in a scholarly journal

Issue

6

Publisher

NATL ASSOC CORROSION ENG