Inhibition efficiency of mixtures of nonionic-ionic surface active agents within aggressive media

V okviru diplomskega dela smo želeli ugotoviti, kako delujejo mešanice površinsko aktivnih snovi v agresivnem kislem mediju. Pri tem so mešanice površinsko aktivnih snovi delovale kot kislinski inhibitorji. Ker nas je zanimalo, kako vplivajo koncentracije inhibitorjev v mešanicah, smo spreminjali njihova razmerja v raztopinah agresivnega medija. Vsaka mešanica inhibitorjev je vsebovala neionsko površinsko aktivno snov (oktil fenol etoksilat) in površinsko aktivno snov ionskega tipa (HTAB ali SDS). Poskuse smo izvedli na vzorcih nerjavnega jekla, katere smo predhodno ustrezno pripravili. Pri eksperimentalnem delu smo uporabili gravimetrično analizo, ki je zajemala tehtanje vzorcev pred in po izpostavitvi neinhibirani ali inhibirani raztopini agresivnega medija. Na nekaterih vzorcih so bile poškodbe, nastale po izpostavitvi neinhibirani ali inhibirani raztopini agresivnega medija dobro vidne, druge manj, zato smo njihovo površino analizirali tudi pod mikroskopom. Za potrditev adsorpcije in tvorbo zaščitnega sloja na površini vzorcev smo uporabili infrardečo spektroskopijo s Fourierjevo transformacijo na oslabljeni totalni odboj (ATR-FTIR). Mešanice neionske-kationske površinsko aktivne snovi so bile učinkovitejše v smislu inhibicije kot mešanice neionske-anionske površinsko aktivne snovi. Inhibicijska učinkovitost mešanic PAS je naraščala z višanjem koncentracije neionskega inhibitorja. Rezultati potrjujejo, da so lahko mešanice površinsko aktivnih snovi bolj učinkovite kot samostojni inhibitorji, vendar je učinkovitost odvisna od narave preiskovanega sistema.This undergraduate thesis presents the corrosion inhibition study of mixtures containing surface active agents in aggressive acidic solvents. The main focus of this thesis was the study of the concentration influence of surface active agents in the mixtures on corrosion inhibition effectiveness. Each mixture contained one non-ionic inhibitor (octylphenol ethoxylate) and one ionic inhibitor (HTAB or SDS). The experiments were carried out on stainless steel samples which were prepared beforehand. The change of mass of the samples was measured before and after the corrosion test. Some of the samples were visibly damaged by the acid. Further investigations of the damage caused by corrosion were made by microscope. Afterwards, the samples were characterised with ATR-FTIR-spectroscopy. The results showed that we have successfully inhibited the samples by adding mixtures of surface active agents to the aggressive acidic solvents. The nonionic-cationic mixture of surfactants inhibited the samples more efficiently than the nonionic-anionic surfactants. The mixtures which had higher concentrations of nonionic surface active agent were more effective than those with lower concentrations. The obtained results proved that the surface active agent mixtures can be more effective than the surface active agents alone. However, the efficiency of the agents depends on their properties