| Highly electrical and thermal conductivities, as well as good mechanical workability of copper and its alloys enable them to have a diverse range of applications in pipelines for domestic and industrial water systems, shipbuilding,seawater desalination and heat exchanger. However, copper and its alloys easily suffer from severe corrosion, especially in the aggressive environment, containing CN-〠Cl-〠NO3- ions. Thus, a considerable amount of efforts have been made to improve the corrosion resistance properties of copper by using effective organic inhibitors with aromatic rings, and electronegative functional groups involving the heteroatoms of sulfur, nitrogen and oxygen, which may adsorb at the copper surface to form inhibitive coatings. Unfortunately, among them, some are toxic. In recent years, various types of nontoxic organic compounds as substitutes for restricted toxic inhibitors have been investigated to regard the interaction with copper.In recent years, pyridine and its derivatives are widely used in food, medicine,chemical industries and many other fields, among them, hexadecylpyridinium chloride(HPC) belongs to the nitrogen cationic surfactants, mainly used for sterilization disinfectant, could chelate with metal through the the π electronic of pyridine ring,is a kind of potential inhibitor.In addition, some hydroxamic acids and their derivatives with biological activities,such as anti–inflammatory and anti–asthmatic are used as pesticides. AHA could form a protection film on copper surface due to multiple adsorption centers(a nitrogen atom and two oxygen atoms)in its structure.Self-assembled monolayers(SAMs) technique as a reasonable method to construct an orderly uniform layers could provide a ideal model for investigating the relationship between inhibitors with copper. SERS(Surface-enhanced Raman scattering) is a highly sensitive technique for probing the adsorption behavior of molecule on metal surface. The SERS information could provide abundant molecular vibration information to clarify the configuration of molecular adsorption.Electrochemical impedance spectroscopy(EIS) technique, a non-destructive, sensitive and informative method has been extensively used as the evaluation of coatings for corrosion inhibition. The electrochemical polarization can provide the corrosion rates from linear polarization and determine the efficiency of corrosion inhibitor.In this work, we used SERS spectroscopy, electrochemical techniques and other methods to investigate the corrosion inhibition behavior of HPC and AHA for copper in aggressive solution. The efficiency against corrosion solution was estimated by electrochemical impedance spectroscopy(EIS) and polarization methods. SERS spectroscopy as a powerful tool to provide molecular fingerprint information was used to elucidate formation mechanism as well as Langmuir adsorption isotherm measurement. Furthermore, quantum chemical studies were used to predict the feasible adsorption centers and confirm the relationship between the molecular structures of inhibitor and its inhibition property.The common approach to the corrosion inhibition of copper are directly adding corrosion inhibitor to corrosion medium(direct charging method). It was further investigated that the corrosion behavior of copper by this method was compared with self-assembly method.Studies have shown that two different corrosion methods have their own characteristic: self-assembled film on the electrode surface is closely packed, the corrosion inhibition efficiency is higher, but it is takes much time to form corrosion film.The film becomes unstable because of contacting with corrosive medium for a long time, and not immediately repaired. Direct charging method is more simple, the corrosive medium contains a certain amount of corrosion inhibitor,the corrosion film can self-repaire immediately after being damaged, so it has an effective protection effect for a long time of contacting with corrosion medium.
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