Techniquefor Anticorrosion Of Copper:Application Of Flavor Ingredients As Green Inhibitors And Self-healing Coatings Based On Dual PH-responsive Nanocapsules

With the awareness of environmental and individual protection,researchers have made great efforts to develop various green corrosion inhibitors in recent years.As reported,plant extract,drugs,and nontoxic surfactants have been developed as eco-friendly corrosion inhibitors for various metals.However,some problems are still needed to be solved.Some flavor ingredients,particularly those edible flavoring substances may be applied as potential green corrosion inhibitors because they are cheap,easilyavailable in both nature and industry and not harmful to human and the environment.The corrosion of the metal may be accelerated by the change of the environment,such as the change of pH value,temperature,and aggressive substances.To prolong the service life of metallic material and reduce the investment in the maintenance of coatings,smart self-healing coatings have also become a hot research topic these days.This dissertation focuses on the two above-mentioned topics and developed some green corrosion inhibitors using flavor ingredients and a dual pH-responsive self-healing polyvinyl butyral?PVB?coating based on mesoporous hollow SiO₂ nanocapsules.As for the green corrosion inhibitors,the corrosion inhibition performances of two thiazole flavors were evaluated.The relationship between their molecular structures and the inhibition performance were also studied.Additionally,for the purpose of enhancing the inhibition efficiency of a cheap flavor?vanillin?and reducing the price of the drug?isoniazide?,a Schiff base was synthesized using the two compounds and employed as a green inhibitor for copper corrosion in NaCl solution.The anticorrosion performance of the product and its raw materials were also evaluated.Another part of this work is the design of a dual pH responsive self-healing coating for protection of copper in Cl-solution.The advantages of this coating can be described as follows: On one hand,unlike most reported smart self-healing coatings,Cerium salt was loaded in the designed nanocapsules and released to form gels with the terpyridine terminated polyol in the coating,which may have a better protective performance than corrosion inhibitors.On the other hand,the healing agent can also be detected by fluorescence,which means that the additional detectable agent is not needed to estimate the loading and release ability of the nanocapsules.The details of thiswork are presented in the following text: 1.Corrosion inhibition for copper in neutral Cl-solution: the effect of two thiazole flavor ingredientsThe influences of two thiazole flavor ingredients on Cu corrosion in NaCl solution were analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy measurements in this part,namely,4-methyl-5-vinylthiazole?MVT?and 5-?2-hydroxyethyl?-4-methylthiazole?HMT?.With the addition of 125 mg/L HMT and 100 mg/L MVT,the inhibition efficiency can reach to 94.09%,according to EIS result.However,the only difference between the two compounds is the functional groups at 5-terminus.Thus,theoretical calculations were conducted to investigate their possible adsorption modes and the relationship between their molecular structures and corrosion inhibition performances.It was revealed that the ethenyl has a more pronounced contribution to electron donation than hydroxyethyl group and the thiazole ring endows the two flavors with the high inhibition efficiencies.2.Corrosion inhibition for copper in neutral Cl-solution: the effect of two thiazole flavor ingredientsTo enhance the anticorrosion ability of flavor?vanillin?and reduce the cost of the drug,a Schiff base?IM?was synthesized and studied as acorrosion inhibitor for corrosion of copper in NaCl solution.The corrosion inhibition efficiency of IM was 93% at the concentration of 120 mg/L,which was much higher than that of the two raw materials at the same dosage.The synthesis of Schiff base may also be applied to other flavors with-CHO group and other drugs with the prime amino group.3.The design of self-healing coatings based on dual pH responsive SiO₂ nanocapsules for anticorrosion of copperA low or high pH value may lead to the acceleration of metal corrosion in the environment.Hence,the self-healing coatings that can respond to the factors are of great benefit to the extension ofits service term.Based on the dissolution of ZnO nanoparticles in the acid or alkaline solution,a self-healing PVB coating integrated with SiO₂ nanocapsules was fabricated,which can release Ce³⁺ as healing agents.The healing agents can form strong gels through the interaction of Ce³⁺ and the terpyridine terminated polyol in the PVB coating,which has a better protection than the films formed by corrosion inhibitors.It was revealed that the release ability of the nanocapsule was stronger in an acidic environment than that in the alkaline environment,and the nanocapsule based PVB coatings had a good anticorrosion performance.