Schreyer T Suter L Eng H Bhni

Contents

1 Introduction 200

1.1 Passivity and local breakdown 200

1.2 Principle of microelectrochemical measurements 201

1.3 Investigation of local tunneling barrier heights 202

2 Experimental 202

2.1 Material and sample preparations 202

2.2 SPM equipment 203

2.3 Microelectrochemical equipment 204

3 Results 205

3.1 Passivation (STM measurements) 205

3.2 Inclusions 207

4 Conclusions 211

5 Outlook 212

6 References 213

Summary. The corrosion resistance of stainless steel is mainly caused by heterogeneities. Inclusions especially play a key role as potential initiation sites. Since most of the electrochemical techniques provide only average data integrating over a relatively large surface area (square millimeters to square centimeters) they are inadequate for studying localized corrosion processes. Use of in-situ scanning probe microscopy (SPM, e.g., scanning tunneling micrsocopy (STM), atomic force microscopy (AFM)) and tip-sample distance modulation spectroscopy in conjunction with microelectrochemical techniques with a current detection limit of <10 fA enables investigations in the nano- and micrometer range.

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