Corrosion Protection Of Copper By A Self-Assembled Monolayer Of Schiff Bases

The corrosion and protection of copper have been always the important studied, fields in corrosion science for many years. Corrosion inhibitors are effective to protect copper. Self-Assembled Monolayer (SAM) is one of the most popular studied fields of interlace chemistry and material science. In electrochemical field, the SAM is an ideal model for further study such as electron transfer, surface electrochemistry, molecular recognition because of its high-order, compact and stability.In order to search good and effective organic corrosion inhibitors, a series of schiff bases were just synthesized. Self-assemble momolayers of Schiff bases were formed on a copper surface pretreated using different methods and the corrosion protection abilities of the monolayer were evaluated in an 0.5M sodium chloride(NaCl) solution or 0.5M HC1 solution using electrochemical techniques. The primary results are as follows:☆ The effects of the monolayer formation such as surface state of copper, self-assembly time, Schiff bases' concentration were measured using electrochemical impedance spectroscopy (EIS) .It shows that the schiff bases can quickly form on the copper surface and have high protection capacity. HNO₃ etching of copper electrode before self-assembly can improve the quality of schiff bases SAM. An increase in immersion time and schiff bases' concentration, undoubtedly improve the coverage .A fairly dense monolayer was formed on copper surface after 2h immersion in 1mM schiff bases.☆ The relationship between schiff base structure and corrosion inhibition efficiency was studied by EIS and quantum chemical calculation. The results show that the nitrogen atom in the -C=N- groups and the oxygen, atom in -OH groups are the mainly reaction groups. The schiff base and copper come into being chelate through II bond and feedback II bond. That schiff bases have high efficiency not only in HC1 solution, but also in NaCl solution. If the molecule of schiff base has bigger conjugate n bonds among the aromatic rings than other schiff base, it will show higher inhibition efficiency.☆ The variation of temperature not only affects the corrosion of copper, but also changes the absorption of schiff base on copper surface, A relative coverage was highest when the schiff base solution was 30 ℃. The Corrosion rate increased with the improving temperature of NaCl solution. The apparent activation energy of corrosion and corrosion inhibition is 38.08 kJ/mol.☆ The corrosion of copper was also affected by the kind of corrosion solution, but the schiff bases have good corrosion inhibition efficiency in wide acidity range of NaCl solution.