Investigation of phenol-formaldehyde resins as corrosion impeding agent in acid solution

Abstract

The advent of organic molecules as inhibitors in the field of corrosion monitoring has been exponentially expanding in the past few years which enhanced the scope for innovation in polymers as potential corrosion inhibitors. The current research focused on the development of azomethine functionalised benzothiazole moiety containing four phenol-formaldehyde resins designated as PF1, PF2, PF3, and PF4; with the aim to combat impending degradations due to corrosion of low carbon containing steel in corrosive acid medium. The present work comprises empirical gravimetric and electrochemical techniques for analysing corrosion inhibition behavior of the developed resins, followed by subsequent surface characterization employing different analytical procedures. The synthesized polymeric resins performed as efficient corrosion inhibiting additives. Its anti-corrosion performance was found in the order: PF4 > PF2 > PF1 > PF3, established from all the experimental findings. It is revealed that the substitution in the benzene unit of benzothiazole moiety played crucial role in corrosion inhibiting mechanism. The activation energy steadily increased after addition of resins into the corrosive medium suggested that this elevated barrier is required to be crossed for the occurrence of corrosion phenomenon, which leads towards declining of corrosion rate. The application of phenol-formaldehyde resins in acid media substantially prevented carbon steel from deterioration due to corrosion. This is attributed to the corrosion inhibiting nature of the adsorbed resin, whereas, the adsorption of resins was confirmed by surface analysing techniques like SEM-EDX, AFM and XPS. Furthermore, these wet-chemical experimental outcomes are well complemented from results analysed from ab initio DFT study and MD simulation. Additionally, MD simulation outcomes helped in visualization of the adsorbed configuration of the modeled resins in presence of different corrosive components.