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

Highlights: • Anodic corrosion protection of SAMs on Au with varying hydrophobicity are compared. • Intermolecular forces control the behaviour of SAMs during anodic polarization. • Hydrophobic SAM enhances corrosion resistance via micelle formation at interface. • Hydrophilic SAM remains weakly surface bound as a highly mobile layer. 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 in situ electrochemical AFM and a 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.