Corrosion inhibition of 5052 aluminium alloy by ascorbic acid : diploma thesis

Primjenom polarizacijskih metoda i elektrokemijske impedancijske spektroskopije ispitana je mogućnost inhibicije korozije 5052 aluminijske legure (AlMgCr) pomoću askorbinske kiseline (u granicama od 110 -6 do 110 -2 M) u 0.5 M NaCl otopini pri 20 o C. Određeni su korozijski potencijali, korozijska struja, polarizacijski otpor, otpor prijenosu naboja, kapacitet površinskog sloja i difuzija kroz površinski sloj. Izračunata je pokrivenost površine molekulama inhibitora te djelotvornost inhibicije korozije. Dobiveni rezultati su pokazali da askorbinska kiselina učinkovito usporava koroziju AlMgCr legure u kloridnoj otopini uz djelotvornost od  92 %. Nadalje, ustanovljeno je da askorbinska kiselina pripada miješanom tipu inhibitora s pojačanim utjecajem na anodnu reakciju. Mehanizam adsorpcije ispitivanog inhibitora opisan je Frundlichovom adsorpcijskom izotermom. Dobivena vrijednost za standardnu slobodnu energiju adsorpcije u iznosu ≈ -10 kJ mol -1 ukazuje na fizikalnu adsorpciju askorbinske kiseline na površinu AlMgCr legure u NaCl otopini. The corrosion inhibition performance of the ascorbic acid (in range from 110 -6 to 110 -2 M) on 5052 aluminium alloy (AlMgCr) corrosion in neutral 0.5 M solution at 20 o C was investigated using potentiodynamic and electrochemical impedance spectroscopy measurements. Corrosion potential, corrosion current, polarization resistance, charge transfer resistance, capacity of surface layer, and diffusion through the surface layer were determined. The surface coverage of the inhibitor molecules and inhibition efficiency were calculated. The obtained results show that ascorbic acid effectively inhibited the corrosion reaction of AlMgCr alloy in the chloride solution with an inhibition efficiency of up to  92 %. Furthermore, ascorbic acid was found to function essentially as a mixed type with a higher influence on anodic reaction. The adsorption behaviour of investigated inhibitor can be described by the Frundlich adsorption isotherm. The adsorption free energy closes to -10 kJ mol -1 indicates physical adsorption of the ascorbic acid on AlMgCr aluminium alloy surface in NaCl solution.