Study on inhibition performance of extracted polysaccharides from mint leaves for pickling of carbon steel
Polysaccharide(EPM)was extracted and separated from mint leaves using water as extractant and ethanol as precipitator,which was used as corrosion inhibitor for pickling of carbon steel.The corrosion inhibition performance of EPM on carbon steel was tested using weight loss method in 2 mol·L-1 HCl aqueous solution at temperature range of 20‒60℃.The results showed that EPM had a certain inhibitory effect on the corrosion of carbon steel in 2 mol·L-1 HCl aqueous solution.With the increase of EPM concentration,the corrosion inhibition efficiency increased.The inhibition efficiency was relatively stable when the concentration of EPM reached 320 mg·L-1.The maximum efficiency was 89.45％when the temperature was 20℃ and EPM concentration was 400 mg·L-1.The corrosion inhibition efficiency of EPM decreased with the increase of pickling temperature.The inhibition efficiency decreased to 49.39％when the temperature was 60℃ and EPM concentration was 400 mg·L-1.According to the comprehensive analysis of thermodynamics and kinetics,the inhibition effect of EPM was attributed to the formation of a single molecular adsorption layer on the surface of carbon steel,which followed the Langmuir adsorption model.It was an exothermic process with the coexistence of physical adsorption and chemical adsorption.The apparent activation energy(Ea)of the corrosion process of carbon steel with EPM in HCl aqueous solution was increased.The inhibition effect of EPM and the extract of mint leaves(EM)on carbon steel were compared.It was found that the inhi-bition performance of EPM was better than that of EM at room temperature.When the corrosion temper-ature was above 40℃,the inhibition performance of EPM decreased and was lower than that of EM.
extract from mint leavespolysaccharidecorrosion inhibitorweight loss method
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