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In situ electrochemical scanning tunneling microscopy (ECSTM) was applied to analyze the local susceptibility to corrosion at different grains of cryogenically rolled microcrystalline copper in a HCl solution, and combined with electron backscatter diffraction (EBSD) and field emission scanning electron miscroscopy (FE-SEM) to discuss the relationship between nanometer scale corrosion resistance and crystallographic orientation. The results show that the thickness of the air-formed oxide layer is grain-dependent with the largest values exceeding locally by a factor of 2 the macroscopic value (2.8 nm) measured electrochemically. Anodic dissolution is also grain-dependent with dissolving grains observed to neighbor corrosion-resistant grains. A nearly random texture prevented an EBSD-based assignment of the crystallographic orientation of the grains observed by ECSTM. However, comparison of the etched surface morphology measured in situ by ECSTM and ex situ by FE-SEM suggested that the faster dissolving grains were oriented closer to ⟨111⟩//ND or in between ⟨111⟩//ND and ⟨110⟩//ND while the neighboring corrosion-resistant grains were oriented closer to ⟨001⟩//ND. The higher step density measured by ECSTM on the grains corroding faster despite possibly ⟨111⟩//ND oriented terraces confirms the role of surface defects related to misorientation on the corrosion susceptibility.

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Different thermomechanical processes have been used to modify the microstructure of elelctrolytic tough pitch copper (ETP-Cu) in terms of texture, mean grain and grain boundary length fraction. Electron backscatter diffraction (EBSD) and linear sweep voltammetry measurements were performed to study the relation between the macroscopic electrochemical behaviour and the microstructure. FE-SEM was used to visualise the surface after the potentiodynamic scans. The results indicate that there is only a small influence of the microstructure on the global electrochemical response of pure copper. The previously reported influence of the crystallographic orientation and grain boundary characteristics on the local corrosion behaviour of pure copper are not clearly reflected in the macroscopic electrochemical response

When aiming for an increased and more sustainable use of metals a thorough knowledge of the corrosion phenomenon as function of the local metal microstructure is of crucial importance. In this work, we summarize the information presented in our previous publications [1][2][3] and present an overview of the different local (electrochemical) techniques that have been proven to be effective in studying the relation between different microstructural variables and their different electrochemical behavior. Atomic force microscopy (AFM)[1], scanning electrochemical microscopy (SECM) [2], and electrochemical scanning tunneling microscopy (EC-STM) [3] were used in combination with electron backscatter diffraction (EBSD). Consequently, correlations could be identified between the grain orientation and grain boundary characteristics, on the one hand, and the electrochemical behavior on the other hand. The grain orientation itself has an influence on the corrosion, and the orientation of the neighboring grains also seems to play a decisive role in the dissolution rate. With respect to intergranular corrosion, only coherent twin boundaries seem to be resistant.