AN INSIGHT TO THE FACTORS INFLUENCING CORROSION UNDER A DROPLET ON STEEL AND GALVANIZED STEEL

The protection of steel and galvanised steel from corrosion is crucial for sustainability, mainly due to the significant carbon footprint associated with the automotive and construction industries, which produce substantial amounts of steel annually. While direct corrosion costs are often considered, the indirect costs resulting from corrosion failures are often overlooked. Therefore, it is imperative to prioritise corrosion mitigation strategies. Protective coatings and corrosion inhibitors are commonly employed to prevent corrosion in steel. However, existing studies primarily focus on using inhibitors in bulk volume electrolytes, neglecting the corrosion protection mechanisms specific to droplet volumes. Droplet corrosion refers to the phenomenon where oxygen depletion at the centre of a droplet, compared to its edges, creates an oxygen gradient within the droplet, leading to corrosion. Since this corrosion mechanism differs significantly from bulk volume corrosion, the effectiveness of corrosion inhibitors may vary accordingly. Various factors, including pH, secondary spreading, relative humidity, salt load density, and others, influence the occurrence of corrosion under droplets. Unfortunately, there is a lack of research on the mechanisms of droplet corrosion and its impact on the efficiency of corrosion inhibitors. To bridge this research gap, this study proposes a rapid electrochemical test method to evaluate the performance of different inhibitors under various conditions specifically related to droplet corrosion. Furthermore, the study delves into a detailed examination of how pH, droplet size, and relative humidity affect the effectiveness of corrosion inhibitors in combating droplet corrosion.