A model study on controlling dealloying corrosion attack by lateral modification of surfactant inhibitors

Shova Neupane,Nicolás A Rivas,Andreas Terfort,Andreas Stierle,Heshmat Noei,Jan D’Haen,Daniel Crespo,Frank Uwe Renner,Anton Kokalj,Patricia Losada-Pérez,Thomas F Keller,Michael Rudolph,Oscar Bertran

doi:10.1038/s41529-021-00169-2

Abstract

Detrimental corrosion is an ever-concerning challenge for metals and alloys. One possible remedy is to apply organic corrosion inhibitors. Despite progress in molecular assembly and inhibitor research, better mechanistic insight on the molecular level is needed. Here we report on the behavior of well-defined artificial molecular interfaces created by micro-contact printing of thiol-inhibitor molecules and subsequent backfilling. The obtained heterogeneity and defects trigger localized dealloying-corrosion of well-defined Cu3Au surfaces. The stability of applied inhibitor molecules depends on alloy surface morphology and on intermolecular forces of the molecular layers. On extended terraces, dealloying preferentially starts at the boundary between areas composed of the two different chain-length inhibitor molecules. Inside of the areas hardly any nucleation of initial pits is visible. Step density strongly influences the morphology of the dealloying attack, while film heterogeneity avoids cracking and controls molecular-scale corrosion attack. The presented surface-science approach, moreover, will ultimately allow to verify the acting mechanisms of inhibitor-cocktails to develop recipes to stabilize metallic alloy surfaces.

Highlights

Wet corrosion and laterally heterogeneous molecular interfaces both pose severe challenges for characterization[1], which becomes a pivotal challenge to further advance materials stability
Various organic inhibitors are used, in part, because of their “autophobic” behavior and capacity to form self-assembled monolayers[2] (SAMs). These amphiphilic assemblies are formed by spontaneous adsorption, and such surfactant inhibitors have been widely employed[2,3,4,5]
Bare alloy surfaces were here prepared by sputtering with Ar+ and annealing cycles in ultra-high vacuum (UHV)

Summary

Introduction

Wet corrosion and laterally heterogeneous molecular interfaces both pose severe challenges for characterization[1], which becomes a pivotal challenge to further advance materials stability. While clean alloy surfaces show a laterally very homogeneous dealloying process[9,12], an adsorbed continuous inhibitor film triggers a heterogeneous, localized corrosion behavior developing micrometer-sized nanoporous pits and initial cracks on the surfaces[15].

Results

Conclusion