A novel and facile strategy to inhibit corrosion: Thiol-click synthesis of polythiols and their skinning on a metal surface to form super thick protective films

Small molecule inhibitors only form thin films that are composed of a single molecule layer or multiple molecule layers. Polymer inhibitors also cannot form thick or stable films due to the lack of crosslinking. Thus, these inhibitors are unable to provide robust protection for copper against corrosion. Inspired by the "skinning" phenomenon that is often met during the use of polythiol curing agents, we developed a novel and facile strategy that involves the skinning of polythiols on copper to form super thick protective films. Three types of polythiols, named SPT, TPT and LTPT, were prepared via thiol-click chemistry. Upon immersing bare copper into the solutions of the polythiols, Cu-S bonds immediately form to anchor the polythiol chains firmly on the copper surface, and the following Cu²⁺ catalysed S-S bond formation reaction leads to crosslinking and film formation. For SPT, TPT and LTPT, the film thicknesses were 2.03, 1.16 and 2.88 μm, and a very high inhibition efficiency of 99.81%, 99.96% and 99.68%, respectively, was achieved in 60 min. Neutral salt spray experiments demonstrated that the polythiol films provide excellent protection for over one week, whereas the control copper samples employing benzotriazole and 1-dodecanethiol suffered from severe corrosion in only 4 h. SPT and TPT have a storage problem due to their instability in air, but this problem was solved by using stable LTPT containing latent thiol groups.