Honey as inhibitor of corrosion processes

V okviru diplomskega dela preučujemo inhibitorni vpliv medu kot zelenega inhibitorja na nerjavnem jeklu v kislem korozivnem mediju. Izbrali smo tri vrste medu, in sicer: kostanjev, cvetlični in akacijev med. Ker nas je zanimalo kako vplivajo različne koncentracije inhibitorjev na stopnjo zaščite, smo spreminjali njihove koncentracije ob dodatkih v kisli medij. Izbrane koncentracije dodatka inhibitorjev so bile: 1-%, 2-% in 4-% dodatek. Izbrana kisla korozijskega medija sta bila 3,5-% raztopina NaCl in simulirana raztopina kislega dežja s pH 3. Meritve smo izvedli na vzorcih nerjavnega jekla AISI 303, ki smo jih predhodno ustrezno pripravili. V nadaljevanju je bila uporabljena klasična elektrokemijska potenciodinamska metoda, s katero smo pridobili rezultate – karakteristične korozijske parametre za nadaljnjo interpretacijo. Površino vzorcev (morfologijo) smo po izpostavitvi neinhibirani in inhibirani raztopini korozivnega medija analizirali prav tako z mikroskopom. Za potrditev adsorpcije in tvorbo zaščitnega filma pa smo uporabili metodo ATR-FTIR. Najvišja dosežena vrednost za inhibicijsko učinkovitost v simulirani obliki kislega dežja s pH 3 je bila v primeru 4-% dodatka medu, in sicer akacijeva vrsta medu (η = 82 %), sledi kostanjev med (η = 80 %), medtem ko je bila le-ta ob dodatku cvetličnega medu okoli η = 63 %. V primeru 3,5-% raztopine NaCl je bila najvišja inhibicijska učinkovitost dosežena ob 2-% dodatku izbranega medu, in sicer: cvetlični med (η = 61 %), akacijev med (η = 60 %) in kostanjev med (η = 50 %). Višja stopnje inhibicije je bila dosežena v korozivnem mediju kisli dež v primerjavi s 3,5-% raztopino NaCl, kar uvršča izbrane vrste medu med potencialne inhibitorje korozijskih procesov v mediju kisli dež. Za 3,5-% raztopino NaCl bi predlagali izbiro drugega inhibitorja, saj glede na nižjo doseženo vrednost inhibicijske učinkovitosti, ne moremo z gotovostjo trditi, da bi izbran inhibitor dovolj učinkovito zaščitil preučevano jeklo pred korozijskimi procesi.In the present bachelor thesis, the inhibitory effect of honey as a green inhibitor on stainless steel in acidic corrosion medium was studied. Three types of honey were chosen: chestnut, wildflower and acacia honey. Since the objective was to study the effects of different inhibitor concentrations on the level of protection, we changed the concentrations upon their introduction in the acid medium. The following concentrations of inhibitors added were: 1%, 2% and 4% addition. The acid mediums used were 3.5% NaCl solution and a simulated acidic rain solution at the pH of 3. The measurements were carried out on pre-prepared samples of stainless steel AISI 303. A classic electrochemical potentiodynamic method was applied to obtain the results – characteristic corrosion parameters – for further interpretation. After the surface of the samples (morphology) was exposed to uninhibited and inhibited solutions of corrosive medium, it was analysed with a microscope. For confirmation of adsorption and formation of the protective film, the method ATR-FTIR was used. The highest value of the inhibition efficacy reached in the simulated acidic rain with pH of 3 was achieved by the 4% addition of honey, namely the acacia type of honey (η = 82%), followed by chestnut honey (η = 80%), whereas with the wildflower honey the value was approximately η = 63%. In the case of 3.5% NaCl solution, the highest inhibition efficacy measured was with the 2% addition of honey: wildflower honey (η = 61%), acacia honey (η = 60%) and chestnut honey (η = 50%). A higher level of inhibition was reached in the corrosive medium acidic rain in comparison with the 3.5% NaCl solution, which classifies the chosen types of honey as potential inhibitors of corrosion processes in the medium acidic rain. For the 3.5% NaCl solution we propose the choice of an alternative inhibitor – regarding the lower value of inhibition efficacy reached, there is no certainty that the chosen inhibitor would sufficiently protect the chosen steel against corrosion processes