Imaging Reactive Sites on a Surface

7 Application Areas of SECM-AFM 17.1.7.1 Imaging Reactive Sites on a Surface 

Further work saw the use of SECM-AFM in conjunction with in situ AFM and Kelvin probe microscopy to examine and interpret the localized corrosion behavior of two aluminum alloys, EN AW-3003 and Al-Mn-Sr-Zr, which are commonly used as heat exchangers [55]. It was found that the Al-Mn-Sr-Zr alloy contained a smaller number of intermetallics with larger Volta differences, compared to the EN AW-3003 alloy. This correlated well with the SECM-AFM images that showed that the EN AW-3003 alloy was significantly more corrosion active, resulting in higher material loss during dissolution. 

More detailed work on the EN AW-3003 alloy was carried out with the sample held under both cathodic and anodic controls [53,54]. For the former, the redox mediator Fe(CN)6 was added to allow electrochemical visualization of cathodically active sites. Importantly, SECM-AFM measurements at cathodic and anodic polarizations revealed both enhanced cathodic and anodic activities, on the surface, and in the vicinity of some of the large intermetallics. 

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