Assessment of new designed surfactants as eco-friendly inhibitors for the corrosion of steel in acidic environment and evaluation of their biological and surface features: thermodynamic, kinetic and mechanistic aspects

Carbon steel is generally exposed to corrosion in acidic media, thus three nonionic surfactants based on pyrazolopyrimidine derivatives were designed and examined for the first time as inhibitors for carbon steel corrosion in 1.0 M HCl solution. The structures of the synthesized pyrazolopyrimidine derivatives and the surfactants were identified using FT-IR, 1H NMR, and 13C NMR. The inhibition efficiencies (%IEs) of the examined surfactants were set to vary with the structures and concentrations of the designed surfactants. The potentiodynamic polarization experiments indicated that the surfactants proceed as mixed-kind inhibitors with chief anodic ones. Mass-loss studies revealed that the %IEs decreased with rising temperature. The obtained great %IEs (around 90% at 500 ppm) of the designed surfactants were interpreted via strong adsorption of the surfactant molecules on the carbon steel surface and construct a protecting film. The adsorption was set to follow the Langmuir adsorption isotherm. The evaluated thermodynamic parameters sustained the physical nature of the adsorption process. The kinetics of corrosion inhibition by these surfactants were negative fractional-first order reactions. The mechanisms of carbon steel corrosion in HCl media and its inhibition by the designed surfactants were suggested. The investigational outcomes acquired from all utilized techniques are agreeable with each other. The designed surfactants were set to have biological activities and useful surface properties, which makes them have the potential ability to treat various diseases and can be employed in a variety of industrial applications.