The communication within particle agglomerates in industrial alloys can have significant impact on the macroscopic reactivity, putting a high demand on the adaptation of wide-field methodologies to clarify this phenomenon. In this work, we report the application of correlated optical microscopies probing operando both local pH and local surface chemical transformation correlated with identical location scanning electron microscopy to quantify in-situ the structure-reactivity of particle agglomerates of foreign elements in Al alloy. The optical operando analyses allow (i) to reveal and quantify the local production of OH- from proton and oxygen reduction at individual Si- or Fe-rich microparticles and (ii) to quantify (and model) the chemical communication between these active sites, within a few µm range, on the local chemical transformation of the material. Wide-field image analysis highlights the statistical importance of the chemical communication that may introduce a new conceptual framework for the understanding the mechanisms in related fields of charge transfer, electrocatalysis and corrosion.
A new Figure 4 has been added, providing additional examples of chemical communication, which is discussed in detail in the newly added Section 3.4