Surface active properties of gelatin and their effect on the electropolishing and corrosion behavior of steel in orthophosphoric acid

• The studied gelatin revealed good surface active properties.
• Improvement produced in EP by the studied gelatin was due to the adsorption of such agents on the anode surface.
• In the presence of gelatin, the solution appeared hopeful, and a distinct improvement in the finish was noted.

Electropolishing behavior of steel was studied in orthophosphoric acid in the presence of gelatin for improving the finish obtained. This was inspected by surface tension measurement and potentiodynamic polarization by measuring the limiting current in solutions containing different concentrations of gelatin. Gelatin addition to electropolishing solution results in a lower limiting current. The gelatin surface parameters were calculated from its surface tension. The parameters considered include critical micelle concentration (CMC), maximum surface excess (Гmax), minimum surface area (Amin) and effectiveness (πCMC). Thermodynamic parameters of micellization (ΔGmic, ΔSmic) for gelatin were also calculated. Gelatin records greatest reduction of surface tension (effectiveness, πcmc) and higher minimum area (Amin). This behavior agrees with the highest inhibition efficiency results obtained from a potentiodynamic method. Scanning electron microscope (SEM) was used to investigate steel surface after electropolishing in the absence and presence of gelatin. The addition of a higher concentration of gelatin was successful to enhance steel surface quality.