Fabrication of a novel hydrophobic anti-corrosion film based on Eu2O3/stearic acid on steel surface; Experimental and detailed computer modeling studies

Abstract

Metal's corrosion is an important parameter affecting the steel lifetime. Nowadays, because of the widespread industrial applications of mild steel, the corrosion protection of this material has become a challenging item. The modification of the metal surface (i.e., mild steel, MS) via thin hydrophobic layers is one of the most efficient/promising protocols for the improvement of the metal's anti-corrosion properties.In this work, the MS sample surface was treated by a novel thin-film based on the europium (Eu) oxide. Using stearic acid (STA) and palmitic acid (PAA) molecules, a hydrophobic layer was constructed on the Eu-treated sample. The EDS and GIXRD tests were utilized for the analysis of the elemental/phase compositions of the treated and untreated samples. The FE-SEM and AFM tests were used for studying the surface morphology and topography of the treated and untreated samples. The corrosion protection durability of the coated metals was checked via electrochemical approaches, i.e., EIS and potentiodynamic polarization. The EDS/Mapping analysis demonstrated that the europium conversion coating (EuCC) was successfully deposited on the MS surface. Besides, a high concentration of the Eu-containing compounds in the GIXRD patterns proved the sufficient Eu-based conversion coating formation on the sample. The contact angle (CA) measurements displayed that after surface modification with the hydrophobic layer, the CA was drastically improved by about 40%. The FE-SEM micrographs ensured the precipitation of a uniform protective layer without obvious cracks on the MS surface. The Tafel curves illustrated that the EuCC-STA could diminish the steel corrosion by mixed anodic and cathodic inhibition mechanisms. The EIS reports evidence that the existence of the EuCC-STA hydrophobic film could diminish about 66% of corrosion activities during 24 h of iron exposure to the harsh 3.5% chloride media.