Complementary electrochemical ICP-MS flow cell and in-situ AFM study of the anodic desorption of molecular adhesion promotors

TL;DR

This study combines electrochemical ICP-MS and in-situ AFM techniques to analyze how molecular adhesion promoters, specifically thiol-based SAMs, protect gold surfaces from corrosion under anodic conditions, revealing the influence of hydrophilic and hydrophobic properties.

Contribution

It introduces a comprehensive multi-technique approach to understand molecular corrosion protection mechanisms at the interface level.

Findings

Hydrophobic SAMs provide higher protection by detaching under micelle formation.

Hydrophilic SAMs remain intact but offer lower corrosion resistance.

The combined methods reveal the role of intermolecular forces in corrosion protection.

Abstract

Molecular adhesion promoters are a central component of modern coating systems for the corrosion protection of structural materials. They are interface active and form ultrathin corrosion inhibiting and adhesion-promoting layers. Here we utilize thiol-based self-assembled monolayers (SAMs) as model system for demonstrating a comprehensive combinatorial approach to understand molecular level corrosion protection mechanisms under anodic polarization. Specifically, we compare hydrophilic 11-Mercapto-1-undecanol and hydrophobic 1-Undecanethiol SAMs and their gold-dissolution inhibiting properties. We can show that the intermolecular forces (hydrophobic vs hydrophilic effects) control how SAM layers perform under oxidative conditions. Specifically, using \textit{in situ} electrochemical AFM and a scanning-flow cell coupled to an ICP-MS a complementary view on both corrosion resistance, as well as on changes in surface morphology/adhesion of the SAM is possible. Protection from oxidative dissolution is higher with hydrophobic SAMs, which detach under micelle formation, while the hydrophilic SAM exhibits lower protective effects on gold dissolution rates, although it stays intact as highly mobile layer under anodic polarization. The developed multi-technique approach will prove useful for studying the interfacial activity and corrosion suppression mechanism of inhibiting molecules on other metals and alloys.