Effect of an Ethyl Acrylate-Derived Organosilane on the Surface and Protective Properties of Steel

The effect of the functional organosilane ethyl N-[3-(triethoxysilyl)propyl]-β-alaninate (compound 3) on the surface, protective, and interfacial properties of steel was investigated. The compound was characterized by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The modified surface was examined using Raman spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), and X-ray photoelectron spectroscopy (XPS). Protective performance was evaluated by the Akimov drop test, cyclic voltammetry, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization with Tafel analysis, and neutral salt spray testing. XPS confirmed the presence of C, N, O, and Si, with the Si 2p signal at 102.12 eV supporting the presence of oxygen-containing silicon species. At 5 wt.% compound 3, the Akimov protection time increased from 4 to approximately 21 s. The water contact angle increased from 46.50° for untreated steel to 68.54° after modification. Electrochemical measurements showed an increase in charge-transfer resistance from 850 to 1160 Ω cm2 and a decrease in the estimated corrosion rate. After 120 h of salt spray exposure, no clearly visible corrosion products were observed on acrylic paint systems pretreated with 5–8 wt.% organosilane solutions. The pull-off adhesion strength of acrylic paint increased from 0.30 to 0.45 N mm−2 following organosilane pretreatment. These findings support the use of compound 3 as a functional surface modifier and pretreatment layer for improving the adhesion and protective performance of acrylic paint systems.