Premium
Study on localized corrosion mechanism of 2195 Al‐Li alloy in 4.0% NaCl solution (pH 6.5) using a three‐electrode coupling system
Author(s) -
Li J. F.,
Zheng Z. Q.,
Jiang N.,
Li S. C.
Publication year - 2005
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200403824
Subject(s) - dissolution , alloy , corrosion , cathodic protection , materials science , anode , intergranular corrosion , electrode , metallurgy , grain boundary , phase (matter) , coupling (piping) , passivation , chemical engineering , layer (electronics) , composite material , chemistry , microstructure , organic chemistry , engineering
Localized corrosion morphologies of 2195 Al‐Li alloy with various heat treatment in 4.0% NaCl solution (pH 6.5) were investigated, and its corrosion mechanism was studied using a three‐electrode coupling system of α (Al) substituting for the precipitate‐free zone (PFZ), simulated bulk θ′ (Al 2 Cu) and T1 (Al 2 CuLi). θ′ acts as cathodic zone in the alloy. At the initial stage, T1 phase is active with respect to θ′ and α (Al), and endures the main anodic current, indicating that anodic dissolution occurs on T1. However, its potential moves to positive direction with immersion time, due to dealloying of Li from T1. As a result, the main anodic dissolution occurs on α (Al) at a later stage. At this stage, as only T1 and α (Al) are coupled, T1 is cathodic to α (Al). In real 2195 alloy, T1 phase is very tiny, and anodic dissolution of T1 and PFZ occurs alternately. These results show that its intergranular corrosion or intersubgranular corrosion is caused by alternate anodic dissolution of T1 phase and PFZ along grain and subgrain boundaries.