Impact of droplet conditions on corrosion inhibitor mechanisms: A case study on small azole molecules

This study investigates the differences in corrosion inhibitor performance between droplet and bulk volumes using a novel electrochemical cell setup that accommodates both environments. Steel and galvanised steel, widely used in the automotive and construction industries, face significant corrosion challenges, with droplet corrosion presenting unique mechanisms compared to bulk volume corrosion. In droplet corrosion, oxygen gradients form due to oxygen depletion at the droplet centre, promoting uniform or localised corrosion based on factors such as salt concentration and droplet size. Despite its relevance, droplet corrosion remains understudied, particularly in the context of inhibitor performance. This study addresses the gap by employing a rapid electrochemical testing method and a database with a wide range of azole derivative structures to evaluate how corrosion inhibitor structures and the working mechanism of corrosion inhibitors affect corrosion protection in varying droplet volumes. Findings from this research are anticipated to enhance corrosion mitigation strategies and promote more effective use of inhibitors in real-world applications. • Corrosion inhibitors show varying performance in droplet and bulk volumes, needing targeted designs • Multi-atom inhibitors show unique interactions; three-sulphur inhibitors may accelerate corrosion • Cathodic inhibitors often lose effectiveness in oxygen-rich droplet conditions • Sustaining inhibitor efficiency in droplets is vital as performance declines over time