Title Derivati benzimidazola kao inhibitori korozije Title (english) Benzimidazole derivatives as corrosion inhibitors Author Martina Mumelaš Mentor Helena Otmačić Ćurković (mentor)Committee member Helena Otmačić Ćurković (predsjednik povjerenstva)Committee member Marijana Kraljić Roković (član povjerenstva)Committee member Marijana Hranjec (član povjerenstva)Granter University of Zagreb Defense date and country 2018-07-13, Croatia Scientific / art field, NATURAL SCIENCES Abstract Morska voda je korozivan medij koji štetno utječe na brojne metalne konstrukcije koje se primjenjuju u građevinarstvu i industriji, a time uzrokuje znatnu gospodarsku štetu i onečišćuje okoliš. Unatoč tome što se u morskom okolišu često primjenjuju korozijski otporne legure poput nehrđajućeg čelika i legura bakra i nikla koje karakterizira mogućnost spontanog formiranja zaštitnog sloja oksida na metalnoj površini, poželjno je koristiti neku vrstu zaštite sa svrhom produljenja vijeka trajanja konstrukcije. U zatvorenim sustavima često se koriste inhibitori korozije, tvari anorganskoga ili organskoga podrijetla koje, dodane u malim količinama u agresivni medij, mogu u velikoj mjeri smanjiti brzinu korozije metala. Njihova učinkovitost ovisi o vrsti inhibitora, korozijskom mediju, temperaturi te koncentraciji. Organski se inhibitori adsorbiraju na metalnu površinu ili reagiraju s korozijskim produktima na površini pritom tvoreći zaštitni sloj, uglavnom zbog prisustva polarnih funkcionalnih skupina u molekulskoj strukturi. Među najučinkovitije spojeve za inhibiciju korozije bakrenih legura ubrajaju se oni koji sadrže heteroatome poput sumpora, dušika, kisika i fosfora. Jedan od glavnih organskih inhibitora korozije korišten za zaštitu bakra i njegovih legura je benzotriazol (BTA)1, heterociklički spoj s dušikom. Osim benzotriazola ispitivane su i efikasnosti brojnih drugih organskih inhibitora poput brojnih derivata imidazola, triazola, amina i aminokiselina 2,3. Većina komercijalnih inhibitora, kao i benzotriazol nije ekološki prihvatljiva pa se sve više istražuju spojevi koji su ekološki prihvatljivi. Cilj ovog rada bio je ispitati i usporediti djelotvornost zaštite legure Cu-Ni dodatkom različitih derivata benzimidazola (2-amino-5(6)-nitrobenzimidazol, 2-amino-5(6)-cijanobenzimidazol, 2-aminobenzimidazol, 2-amino-5(6)-(2-imidazolinil)-benzimidazol hidroklorid), u umjetnoj morskoj vodi (3 %-tna NaCl otopina). Brzina korozijskih procesa određivana je metodom Tafelove ekstrapolacije kojom je pokazano da je najdjelotvorniji inhibitor 2-amino-5(6)-nitrobenzimidazol koji pri koncentraciji 10^-3M pokazuje inhibitorsku djelotvornost od 71 %. Potom su provedena elektrokemijska ispitivanja u vremenu za dva najdjelotvornijih inhibitora, metodom linearne polarizacije i metodom elektrokemijske impedancijske spektroskopije (EIS). Površine uzoraka analizirane su pretražnim elektronskim mikroskopom i spektroskopski FTIR-om. Zaključujeno je da djelotvornosti inhibitora pridonosi dulje vrijeme izlaganja uzoraka otopinama inhibitora kao i veće koncentracije.
Abstract (english) Seawater is a corrosive medium that adversely affects the numerous metallic constructions used in construction and industry and thus causes significant economic damage and pollutes the environment. Despite the fact that corrosion resistant alloys such as stainless steel and copper and nickel alloys are often used in the marine environment, which are characterized by the possibility of spontaneous formation of a protective layer of oxide on a metal surface, it is desirable to use some type of protection to extend the life of the structure. In closed systems, corrosion inhibitors, substances of inorganic or organic origin are often used which, when added in small quantities to an aggressive medium, can greatly reduce the corrosion rate of metal. Their efficacy depends on the type of inhibitor, the medium to which the inhibitor is added, the temperature and concentration. Organic inhibitors are adsorb on the metal surface or combine with corrosion products on the surface while forming a protective layer, mainly due to the presence of polar functional groups in the molecular structure. Among the most effective inhibitors of corrosion of copper alloys are those containing heteroatoms such as sulfur, nitrogen, oxygen and phosphorus. One of the major organic corrosion inhibitors used to protect copper and its alloys is benzotriazole (BTA)1, a nitrogen heterocyclic compound. In addition to benzotriazole, the efficacy of numerous other organic inhibitors, such as derivatives of imidazoles, triazoles, amines and amino acids.2,3 Most commercial inhibitors, like benzotriazole, are not ecologically acceptable, so new ecologically acceptable compounds are being investigated. The aim of this work was to examine and compare the efficacy of Cu-Ni alloy protection by various benzimidazole derivatives (2-amino-5(6)-nitrobenzimidazole, 2-amino-5-(6-cyanobenzimidazole, 2-aminobenzimidazole, 2-amino-6)-(2-imidazolinyl) benzimidazole hydrochloride) in artificial seawater (3 % NaCl solution). The corrosion rate was determined by Tafel's extrapolation method, which showed that the most effective inhibitor is 2-amino-5 (6) -nitrobenzimidazole at a concentration of 10^-3M exhibits an inhibitory effect of 71 %. Then the electrochemical tests were performed in time for the two most effective inhibitors (linear polarization method and electrochemical impedance spectroscopy (EIS) method.) The surface of the samples was analyzed by scanning electron microscopy and spectroscopic FTIR. It was concluded that the efficacy of the inhibitor increases with prolonged exposure to the inhibitor solutions as well as with increase of inhibitor concentrations.
Keywords
korozija
zaštita
legura CuNi
organski inhibitori
derivati benzimidazola
Keywords (english)
corrosion
protection
CuNi alloys
organic inhibitors
benzimidazole derivatives
Language croatian URN:NBN urn:nbn:hr:149:144142 Study programme Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2020-07-16 13:15:03
