Comparative Studies of Two Chitosan Schiff Bases as Green Corrosion Inhibitors for Cylindrical Copper in 1 M HCl

Purpose The purpose of this study is to prepare CS-TiO2/salicylaldehyde Schiff bases using two different molecular weights of chitosan (CS): low molecular weight and medium molecular weight were used to prepare CS-TiO2/salicylaldehyde Schiff bases and investigate these two compounds, as corrosion inhibitors for copper in 1 M HCl solution using electrochemical impedance spectroscopy and cyclic potentiodynamic polarization measurements. Design/methodology/approach CS-TiO2/salicylaldehyde Schiff bases using two different molecular weight of CS were prepared first by mixing CS in 10% acetic acid (10 mL) with TiO2, second adding salicylaldehyde to the solution with modifying pH of the medium to 6 by using (2 M) of NaOH, product was obtained by filtration and washed several times to get rid of any unreacted salicylaldehyde. Four different concentrations were prepared: 50, 100, 200 and 500 ppm to study the corrosion inhibitor properties of CS-TiO2/salicylaldehyde Schiff bases. Findings Fourier transform infrared spectroscopy analysis indicates that the characteristic peak of the -NH2 group in CS disappeared, confirming the reaction between amine groups in CS and the aldehyde group in salicylaldehyde, which indicates the formation of Schiff base. X-ray diffraction analysis confirms the formation of CS-TiO2/salicylaldehyde Schiff bases; the TiO2 crystallinity did not affect during Schiff base formation. Thermogravimetric analysis shows an improvement in thermal behavior in CS-TiO2/salicylaldehyde Schiff bases than in CS itself, with a maximum degradation rate found to be at 355.2°C by using the derivative thermogravimetric (DTG) curve. The polarization tests show that the effect of inhibiting the copper corrosion was highly increased in the presence of 100 ppm of low molecular weight CS in CS-TiO2/salicylaldehyde Schiff base than in the presence of 100 ppm of medium molecular weight CS in CS-TiO2/salicylaldehyde Schiff base. The electrochemical corrosion experiments proved that both molecular weights of CS Schiff base exhibited a good inhibiting property for copper in 0.1 M HCl. Low molecular weight CS Schiff base shows better performance as a corrosion inhibitor than the medium molecular weight CS. At 100 ppm concentration, the corrosion current density (jCorr) was lower for the low molecular weight inhibitor (0.69 mAcm−2) compared to (0.90 mAcm−2) for the medium molecular weight. This funding refers to a low molecular weight CS Schiff base that was more effective at slowing down the corrosion process, likely due to its smaller size allows it to better cover and stick to the copper surface, forming a stronger protective barrier against corrosive agents. This result was further confirmed by the analysis of the surface using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The influence of corrosive attack on copper surfaces was examined using an SEM and EDS. Originality/value This study aims to determine which molecular weight of CS Schiff base is the most effective as a corrosion inhibitor. This study will serve as a foundation for future work involving low molecular weight CS Schiff bases and testing their potential as corrosion inhibitor agents on various metals, such as aluminum and steel.