Study on localized corrosion mechanism of 2195 Al‐Li alloy in 4.0% NaCl solution (pH 6.5) using a three‐electrode coupling system

Abstract

Study on localized corrosion mechanism of 2195 Al-Li alloy in 4.0% NaCl solution (pH 6.5) using a three-electrode coupling system 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 a (Al) substituting for the precipitate-free zone (PFZ), simulated bulk h 0 (Al 2 Cu) and T1 (Al 2 CuLi). h 0 acts as cathodic zone in the alloy. At the initial stage, T1 phase is active with respect to h 0 and a (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 a (Al) at a later stage. At this stage, as only T1 and a (Al) are coupled, T1 is cathodic to a (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.

Influence of Post-Welding Heat Treatment on the Corrosion Behavior of a 2050-T3 Aluminum-Copper-Lithium Alloy Friction Stir Welding Joint

“…Galvanic coupling between intergranular T 1 precipitates, which have a corrosion potential that is more negative than that of the matrix, and the surrounding matrix promoted the propagation of intergranular corrosion. 11,13,25 Moreover, the strong grain deformation in the HAZ might significantly contribute to increasing the reactivity of the grain boundaries. The corrosion morphology observed on each metallurgical zone after an OCP measurement on the global welded joint in 1 M NaCl solution was similar to that observed when each zone was exposed to 1 M NaCl individually.…”

“…[8][9][10] Actually, some authors have studied the electrochemical behavior of the precipitates present in the alloy compared to that of the matrix. [11][12][13] They emphasized that the electrochemical behavior of T 1 precipitates changed over time during immersion in 4% NaCl. The T 1 precipitates, that were anodic towards the matrix at the beginning of the immersion test in 4% NaCl, became cathodic towards the matrix after approximately 50 h. The reports stated that it was the alternating dissolution of the T 1 precipitates and the matrix which led to the corrosion behavior observed.…”

“…The authors also studied the cathodic behavior of the h 0 phase and the alternating cathodic and anodic behavior of T 2 towards the matrix. 11,13 The FSW process leads to an increase of the temperature and severe plastic deformation around the weld. Whatever the aluminum alloy welded, a typical friction stir weld consists of unaffected base material (BM), a heat affected zone (HAZ), a thermo-mechanically affected zone (TMAZ) and a dynamically recrystallized zone (DXZ or nugget).…”

Characterisation and understanding of the corrosion behaviour of the nugget in a 2050 aluminium alloy Friction Stir Welding joint

“…Thus, some micro-galvanic coupling phenomena might appear to lead to the dissolution of the particles or the matrix. In addition, the hardening precipitates are very active particles, as mentioned by Li et al [22], who evaluated the electrochemical behaviour of T 1 and h 0 with respect to the matrix and brought to light that the T 1 precipitates had a more cathodic corrosion potential than the matrix in a 4% NaCl solution. Li et al [23] have also studied the evolution of the galvanic coupling between T 1 or T 2 precipitates with the matrix.…”

Síntesis, caracterización y evaluación de la resistencia a la corrosión de recubrimientos híbridos Sol-Gel base TEOS/MPS sobre la aleación AA2050-T8

“…Dentro de las aleaciones de aluminio más utilizadas en dicha industria se encuentran las pertenecientes a la serie AA7xxx (Al-Zn-Mg), que exhiben la mayor resistencia mecánica de todas las aleaciones de aluminio; sin embargo, presentan baja tolerancia al daño (Polmear, 2005;Viejo et al, 2010a). Por otro lado, se encuentran las aleaciones de la serie AA2xxx (Al-Cu) que presentan destacada tolerancia al daño y estabilidad térmica, pero con una menor resistencia mecánica comparada con las aleaciones de la serie AA7xxx (Li et al, 2005;Viejo et al, 2010b).…”