A mixture of dicyclohexylamine and oleylamine as a corrosion inhibitor for mild steel in NaCl solution saturated with CO2 under both continual immersion and top of the line corrosion

Abstract

This paper presents a comprehensive method to evaluate a mixture of dicyclohexylamine and oleylamine (DCHA+OA) as a corrosion inhibitor for mild steel in a CO2 environment in the liquid and vapor phase. The volatile properties of the corrosion inhibitor were investigated in order to determine whether DCHA+OA could be used to control the severity of a top of the line (TLC) corrosion attack. Corrosion measurements were performed using electrochemical impedance spectroscopy, linear polarization resistance, potentio-dynamic sweep measurements, as well as electrical resistance and weight loss measurements, in order to determine the inhibitive performances of dicyclohexylamine and oleylamine. In order to define the surface morphological characteristics, the scanning electron microscopy technique was applied. The electrochemical study and the weight loss measurements indicated that DCHA+OA significantly decreased the corrosion rate in the liquid phase when 50 ppm of DCHA+OA was added. Scanning electron microphotographs indicated a protective inhibitor film was formed on the steel surface and revealed that good protection was achieved, together with a decrease in the corrosion rate, as determined by weight loss and electrochemical techniques. It was shown using electrical resistance measurements in the vapor phase, that a concentration of 1000 ppm DCHA+OA significantly decreased the corrosion rate at the top of the line only when it was carried there within its own foam and not due its volatility.

U ovom radu ispitivana je zaštita niskougljeničnog čelika od korozije pod dejstvom CO2 primenom smese dicikloheksilamina i oleilamina (DCHA+OA) kao inhibitora u tečnoj i gasovitoj fazi. Isparljivost smese DCHA+OA je ispitivana u cilju potencijalne primene DCHA+OA kao lako isparljivog inhibitora za smanjenje brzine korozije u uslovima kondenzacije. Pri ispitivanju inhibitorskih svojstava smese diciklohekcilamina i oleilamina primenjene su sledeće tehnike karakterizacije: spektroskopija elektrohemijske impedancije, metoda linearne polarizacione otpornosti, metoda polarizacije linearno promenljivim potencijalom, merenje električne otpornosti, gravimetrijska metoda određivanja gubitka mase, kao i skenirajuća elektronska mikroskopija. Rezultati elektrohemijskih merenja i gravimetrijske metode određivanja gubitka mase pokazuju da dodata smesa DCHA+OA u koncentraciji od 50 ppm značajno smanjuje brzinu korozije u tečnoj fazi u odnosu na sistem bez inhibitora. Mikrofotografije površine čelika potvrđuju da se u prisustvu smese DCHA+OA smanjuje stepen korozije kao posledica formiranja zaštitnog filma inhibitora na površini niskougljeničnog čelika. Primenom tehnike merenja električne otpornosti u gasovitoj fazi pokazano je da dodatak smese inhibitora DCHA+OA u koncentraciji od 1000 ppm dovodi do značajnog smanjenja brzine korozije u uslovima kondenzacije, samo u slučaju kada se transport inhibitora do površine čelika ostvaruje u obliku pene, a ne zbog isparljivosti samog inhibitora.