An insight into the influence of morphological and compositional heterogeneity of an individual intermetallic particle on aluminium alloy corrosion initiation

Abstract

In this work, a multi‐analytical in situ and ex situ approach was used to provide information needed to identify the role of an individual heterogeneous intermetallic particle (IMP) in localized corrosion initiation of aluminium alloys. The heterogeneity of the IMP was studied by combining atomic force microscopy (AFM), scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS) and scanning electrochemical microscopy (SECM). A complex Al–Mn–Fe–Si IMP phase with different chemical composition in its inner and outer parts was characterized by SEM–EDS analysis. AFM results uniquely revealed a brain‐like feature of an IMP with 20 nm height variations. Submicron sized galvanic cell induced by morphological and compositional heterogeneity resulted in a localized corrosion attack inside the individual IMP. Various collected current levels measured by SECM were associated to the morphological and compositional heterogeneity of IMPs.

Electrochemical profiling of multi-clad aluminium sheets used in automotive heat exchangers

“…However, upon brazing due to the outward diffusion of Cu from the core material, the E corr value of the resolidified clad increases thus lowering the gap between the E corr values of the core and the clad. The formation of Al(Fe,Mn,Cu)Si precipitates which are cathodic in nature when compared to the Al matrix enhances the potential difference between these materials and allows for galvanic coupling and corrosion propagation between the matrix and the precipitates [60][61][62][63][64][65][66][67] even though the overall E corr value is higher.…”

Corrosion of Cast Aluminum Alloys: A Review

“…Al-Si alloys generally suffer localized corrosion in the Al-Si eutectic due to impurities, such as Fe; generally, the corrosion behavior of these alloys depends on the amount and morphology of Fe-rich intermetallics, such as AlFeSi and AlFeSiMg [36]. Both Fe and Si are cathodic with respect to the aluminum, and therefore, together they can form a microgalvanic couple, resulting in localized corrosion, and silicon also increases the corrosion potential [37,38]. The addition of Pb and Cu to Al-Si alloys decreases the corrosion potential and increases current density as has been observed in PM Al-Si alloys.…”

Transformation of iron containing constituent intermetallic particles during hydrothermal treatment

“…In general, the presence of these intermetallic particles in aluminium matrix results in the heterogeneous microstructure, which has a high impact on the corrosion resistance properties of aluminium alloys [15][16][17][18][19]. Thus, aluminium alloys essentially require pre-treatment (well known as conversion coatings) to maintain its corrosion performance with or without polymer coatings such as paints [20][21][22][23][24][25][26].…”