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In the boundary lubrication regime, the addition of long as well as straight alkyl chain containing additive exhibit a serendipitous impact on protecting various metallic surfaces or machinery components from friction and subsequent wear. In quest of environment-friendly, proficient friction-reducing, surface protective and cost-effective lubricant additives; herein, two diazomethine functionalised long-chain consisting organic molecules, namely (3E)-N-((E)-2-(octadecylimino)ethylidene)octadecan-1-amine (ODE) and (3E)-N-((E)-2-(dodecylimino)ethylidene)dodecan-1-amine (DDE) were synthesized through a one-pot condensation reaction. The surface protective film-forming, as well as wear and friction reducing properties of these organic additives on steel balls within paraffin oil (PO), were thoroughly explored using a four-ball tester with variation in time, load and speed. The addition of these additives showed a remarkable reduction of coefficient of friction (COF) and wear amount in compared to the pure base oil. ODE exhibited better performance with a ∼62% reduction in COF and ∼23% reduction in wear amount for steels in contact. Electronic level analysis for elucidating the tribofilm formation capability of the additives was rationalized using computational approaches such as density functional theory (DFT) and Fukui indices. Additionally, the molecular dynamics (MD) simulation which is an efficient computational approach was used to explore the spontaneous adsorption insight of additives; and also radial distribution function (RDF) were analysed to impressively explore the molecular-level interactions and adsorption mechanism of the additives with the metal atoms. Thereby, the mechanism of surface adhesive tribofilm formation and its metal protection capability has been explained in a comprehensive manner. Diazomethine functionalised organic molecules were synthesized with a variation of aliphatic chain length. Long aliphatic chain containing ODE additive showed enhanced surface protective performances in paraffin oil exhibiting lower COF value in comparison to DDE. Possible formation of ODE-based efficient tribofilm in metal-solution interface which exhibits enhanced surface adsorption property on the metal surface. Substantial decrease in wear upon addition of ODE in the base oil, which was confirmed by FE-SEM and 3D surface profilometer study. MD simulation has been used to investigate the adsorption competence of ODE and DDE on the iron surface. [ABSTRACT FROM AUTHOR]

An alkyl and acyl substituted redox-active Schiff bases, namely, 2-(2-hydroxybenzylideneamino)phenol (Inh-1), 2-((2-hydroxyphenylimino)methyl)-4-methylphenol (Inh-2) and 2-((2-hydroxyphenylimino)methyl)4-methoxyphenol (Inh-3) were synthesized and characterised. Afterwards, its anticorrosion aspect for mild steels dipped into 1 molL−1 H 2 SO 4 solution was explored by potentiodynamic polarization as well as electrochemical impedance spectroscopy. These molecules act as excellent corrosion inhibitors to protect mild steels immersed in 1 molL−1 H 2 SO 4 solution. Surface studies were performed by employing FESEM and AFM; while the elemental characterization of mild steels that were exposed in corrosive medium with and without containing the synthesized Schiff base molecules was performed using EDX study. All these studies established the formation of corrosion protecting layer developed over metal surfaces. Adsorption competency of the synthesized inhibitors were studied and explained in details. The spontaneity and nature of adsorption of the synthesized inhibitors were explained based on free energy determined from experimental findings. Additionally, the experimentally obtained corrosion inhibition property as well as adsorption capability were furthermore insightfully explained and correlated with density functional theory and Fukui indices analysis. Also, density functional based tight binding calculation was carried out for visualizing interactions of inhibitors occurring with metal surface atoms favouring its adsorption. Finally, molecular dynamics simulation was employed to envisage the interactions of synthesized inhibitors with metal surface atoms along with corrosive species as it happens in real corrosive environment. Furthermore, the analysis of radial distribution function have been used to elucidate experimentally predicted adsorption behaviour of studied molecules. Unlabelled Image • Redox-active Schiff base act as excellent corrosion inhibitor in 1 molL−1 H 2 SO 4. • Electrochemical study revealed metallic corrosion suppression by these inhibitors. • DFT study unveiled inhibitors' electronic properties susceptible for interaction. • DFTB study revealed interaction leading to inhibitors' adsorption on metal surface. • MD simulation revealed inhibitors' adsorption on metal surface in corrosive medium. [ABSTRACT FROM AUTHOR]